Development and evaluation of habitat suitability models for nesting white-headed woodpecker (Dryobates albolarvatus) in burned forest.

Salvage logging in burned forests can negatively affect habitat for white-headed woodpeckers (Dryobates albolarvatus), a species of conservation concern, but also meets socioeconomic demands for timber and human safety. Habitat suitability index (HSI) models can inform forest management activities to help meet habitat conservation objectives. Informing post-fire forest management, however, involves model application at new locations as wildfires occur, requiring evaluation of predictive performance across locations. We developed HSI models for white-headed woodpeckers using nest sites from two burned-forest locations in Oregon, the Toolbox (2002) and Canyon Creek (2015) fires. We measured predictive performance by developing one model at each of the two locations and quantifying discrimination of nest from reference sites at two other wildfire locations where the model had not been developed (either Toolbox or Canyon Creek, and the Barry Point Fire [2011]). We developed and evaluated Maxent models based on remotely sensed environmental metrics to support habitat mapping, and weighted logistic regression (WLR) models that combined remotely sensed and field-collected metrics to inform management prescriptions. Both Maxent and WLR models developed either at Canyon Creek or Toolbox performed adequately to inform management when applied at the alternate Toolbox or Canyon Creek location, respectively (area under the receiver-operating-characteristic curve [AUC] range = 0.61-0.72) but poorly when applied at Barry Point (AUC = 0.53-0.57). The final HSI models fitted to Toolbox and Canyon Creek data quantified suitable nesting habitat as severely burned or open sites adjacent to lower severity and closed canopy sites, where foraging presumably occurs. We suggest these models are applicable at locations similar to development locations but not at locations resembling Barry Point, which were characterized by more (pre-fire) canopy openings, larger diameter trees, less ponderosa pine (Pinus ponderosa), and more juniper (Juniperus occidentalis). Considering our results, we recommend caution when applying HSI models developed at individual wildfire locations to inform post-fire management at new locations without first evaluating predictive performance.

Introduction

Wildfire influences vegetation structure and composition in dry conifer forests of western North America along with associated biological communities. Many species colonize recently burned forests, where resources generated by wildfire allow populations to proliferate [1, 2]. In particular, woodpeckers and other cavity-nesting species benefit from trees that are killed, injured, or weakened by fire for nesting and foraging [3-5]. Anthropogenic land use and climate change strongly influence wildfire, fire-related ecological processes, and consequently habitat for fire-associated species [6, 7].

Salvage logging in particular negatively impacts fire-associated species by targeting a key resource upon which they depend: relatively large trees killed by fire [4, 5, 8, 9]. Despite broad evidence for primarily negative impacts on biodiversity, managers commonly apply salvage logging to recoup economic loss of timber resources and mitigate human safety hazards following wildfire [10, 11]. Increased size and severity of wildfire with warming temperatures [6, 7] may further increase opportunity and perceived socioeconomic need for salvage logging. Forest managers must therefore balance socio-economic demands with mandates requiring maintenance of post-fire habitat for wildlife.

Researchers use habitat suitability models (sometimes known as species distribution models) to identify suitable habitat and predict species distributions to inform land management decisions aimed at species conservation [12]. These models quantify environmental relationships with known species occurrences, and based on these, predict species distribution. Models often provide habitat suitability indices (HSIs; 0–1 range) that at minimum indicate relative likelihood of species occurrence (0 = least likely, 1 = most likely). Interpretation of HSIs and their value for ecological inference is the subject of ongoing debate and depends at least in part on modeling technique and data used for model development [13-17]. Nevertheless, to inform habitat conservation, models are ultimately expected to discriminate where species are most, versus least likely to occur within relevant areas.

How we develop and evaluate habitat models must reflect both species ecology and intended applications. Often predictive maps that provide continuous and broad coverage are needed to inform conservation and management planning. Models developed for these purposes typically employ environmental variables derived from remotely sensed data [18-20], which are typically coarse in resolution and information content [21]. Thus, restricting models to remotely sensed data can limit performance by limiting their ability to quantify key relationships governing species distributions at finer resolutions [3]. Consequently, including field-measured data can improve performance [3]. Incorporating field-collected data may preclude habitat mapping over broad spatial extents, but may provide finer resolution information useful for management prescriptions to maintain or improve habitat suitability.

Regardless of the particular application, models informing habitat management for fire-associated species must continually be applied to new locations as new wildfires occur [e.g., 22]. Many factors can cause geographic variability in model applicability, however, including biotic interactions, local adaptation, and behavioral rules governing habitat selection [23-26]. Because of funding limitations and the unpredictability of wildfire, models for disturbance-associated woodpeckers typically represent individual wildfire locations [3, 5, 27, except see 28], potentially limiting wider model applicability. Such concerns are common for predictive habitat models [23, 24, 29], raising the need to evaluate applicability across locations to test transferability [ability of models to provide useful predictions when applied at new locations beyond where they were originally developed; [30-32]. Models that consistently describe occurrence patterns throughout a species range can be generally applied to informing management. Conversely, given spatial variability in environmental relationships, comparing predictions across locations can reveal limitations to model applicability [32].

The white-headed woodpecker (Dryobates albolarvatus) is a fire-associated species of conservation concern. The species is endemic to dry, conifer forests of western North America, where habitat loss and degradation due to human activities and consequent alteration of fire regimes has raised conservation concerns [33]. White-headed woodpeckers nest in both recently burned and unburned forests typically within landscapes characterized by mosaics of open- and closed-canopy forests often generated and maintained by mixed-severity fire [27, 34, 35]. In burned forests, nests are typically placed in moderate-to-severely burned or open-canopied sites adjacent to less-burned or closed-canopy areas, which contain greater densities of live trees thought to provide food resources [27]. Additionally, nest cavities are typically excavated in decayed snags within forest stands dominated by ponderosa pine (Pinus ponderosa) in the northern portion of their range. Nest survival can be substantially higher in burned compared to unburned forests, suggesting burned forests could represent source habitat for maintaining populations [27, 34]. Therefore, conservation of burned forest habitats may be particularly important for population persistence, but complex environmental relationships make identifying suitable nesting habitat challenging.

Here, we developed and evaluated habitat suitability models for nesting white-headed woodpeckers in burned forests. Our objectives were 1) to develop models capable of supporting both coarse-resolution habitat mapping and management prescriptions, 2) to evaluate models by testing their transferability across wildfire locations, thereby establishing their broad applicability to inform post-fire forest management.

Materials and methods

Ethics statement

All fieldwork for this study was conducted on public lands. None of our study species were listed as threatened or endangered under the U.S. Endangered Species Act. Data collection was purely observational and did not involve any physical contact with study organisms. All work was conducted following best practices for minimizing observer impacts on nesting birds [36].

Study locations and management

We modeled habitat relationships for nesting white-headed woodpeckers at the Toolbox and Silver fire complex in central Oregon (hereafter the Toolbox Fire; 42°57´N, 120°59´W) and at the Canyon Creek Complex in eastern Oregon (hereafter Canyon Creek Fire; 44°17´N, 118°51´W). We evaluated model predictions by applying models between these and a third location, the Barry Point Fire in southern Oregon (42°04´N, 120°39´W; Table 1, Fig 1). Preliminary analysis revealed different relationships at Barry Point compared to the other two locations, resulting in poor predictive performance when applying Barry Point models at Toolbox and Canyon Creek (V. Saab unpublished data). Considering the limited sample size at Barry Point (n = 19 nest sites), we lacked confidence in relationships observed at Barry Point for contributing meaningfully to general knowledge of white-headed woodpecker nesting habitat relationships. We therefore abandoned model development at Barry Point for this study and used Barry Point data exclusively to evaluate models developed at the other two locations. Before wildfire, all three study locations were characterized as dry mixed-conifer forest, much of which was dominated or co-dominated by ponderosa pine and managed for multiple uses (e.g., wildlife habitat, timber harvest, and grazing).

Table 1

Timing, size, and sampling of three Oregon wildfires where white-headed woodpecker nests were located to develop and evaluate habitat suitability models.

National Forest	Fire Name	Ignition Year	Years surveyed	Full extent (ha)	Surveyed extent (ha)	No. pixels with nestsa
Fremont-Winema	Toolbox	2002	2003‒2007	33,427	856b	46b
Fremont-Winema	Barry Point	2011	2012	12,352c	1,603	19d
Malheur	Canyon Creek	2015	2016‒2017	44,672	4,347, 4,727e	47

aWe treated each pixel containing ≥ 1 nest as one observation for habitat models. We located 47 nests at Toolbox, but two were located in the same pixel.

bNon-nest sites were only measured in the 13 larger of 22 survey units. In these 13 units, area surveyed = 798 ha and 33 nests were located.

cThe Barry Point Fire extended into California, but only the Oregon extent is represented here.

dBarry Point data were used for model evaluation but not development because relationships differed from other study locations, and we questioned the generality of Barry Point relationships considering the limited sample size.

eOne survey unit at Canyon Creek was replaced between years; area surveyed was 4,347 ha in 2016 and 4,727 ha in 2017.

Fig 1

Wildfire locations.

Maps showing the three study locations where habitat suitability models were developed and evaluated for white-headed woodpeckers in burned forests, Oregon, U.S.A.

Salvage logging was implemented in portions of the Toolbox and Canyon Creek Fires. Lands within both fire perimeters were owned by a mix of public (U.S. Forest Service [USFS], Bureau of Land Management, and the state of Oregon) and private entities. Most private property containing merchantable timber was logged immediately following wildfire. Logging activities on USFS lands focused on a priori identified sale units located within a subset of our survey units (described below). Logging prescriptions implemented at the Toolbox Fire retained ≥ 25 snags per hectare of diameters representing the range of pre-treatment tree and snag diameters, and retained snags were distributed in clumps of ≥ 100 snags per 4 hectares [37]. Except for immediately logged private lands, salvage logging was primarily implemented in autumn of 2004 at Toolbox, resulting in increased total logging extent from 2004 to 2005 breeding seasons (375 to 5,946 ha) and a smaller increase from 2005 to 2007 (6,249 ha) within 1 km of study units. At the Canyon Creek Fire, roadside salvage logging was implemented in 2016 before, during, and after nest surveys, wherein 799 ha (283 ha within our survey units) along roads were cleared of standing dead trees identified as hazardous to the public [38]. Between the 2016 and 2017 breeding seasons, additional selective harvest was implemented across 490 ha of surveyed areas, wherein prescribed retention was 84–126 snags of diameter at breast height (DBH) > 23 cm per hectare. Salvage logging was not implemented at the Barry Point Fire. Although wildfire locations included some private land, we restricted surveys to public land.

Nest surveys and reference sites

We surveyed rectangular belt transects spanning a priori established survey units (Table 1, Fig 1) to locate occupied nest cavities [36] during early May until mid-July 1–5 years following wildfire (Table 1). We placed the center of belt transects 200 m apart and surveyed 100 m on either side of the center line. Transects began and ended at opposing unit boundaries, so surveys covered each unit. We surveyed 22 units at Toolbox (2–116 ha), 9 units at Canyon Creek (161–403 ha), and 5 units at Barry Point (164–439 ha). At Barry Point and Canyon Creek, survey units included suitable and unsuitable habitat identified by a preliminary model developed with white-headed woodpecker nest site data from Toolbox (V. Saab unpublished data). We incorporated call broadcasts into our surveys to elicit responses by territorial woodpeckers and thereby improve detection. We used GPS units (Garmin Etrex, Garmin International, Inc, Olathe, KS 66062; Trimble GeoExplorer3, Trimble Navigation Limited 1999–2001, Sunnyvale, CA 94085) to determine the geographic coordinates of each nest cavity. Surveyors typically remained within survey unit boundaries but occasionally strayed up to 250 m outside unit boundaries when following specific individuals exhibiting signs of breeding behavior to locate a nest cavity. Thus, nest sites were occasionally located just outside unit boundaries.

Habitat suitability models compared environmental conditions at nest to reference sites. For models restricted to remotely sensed data, reference sites were 10,000 30-m pixels drawn randomly from within the area surveyed at each wildfire location (hereafter available sites). For models developed with remotely sensed and field-collected data, reference sites were 134, 176, and 21 non-nest sites randomly located within survey unit boundaries at Toolbox, Canyon Creek, and Barry Point locations, respectively. We centered non-nest measurements on the tree nearest to each randomly generated coordinate and then re-measured non-nest coordinates in the field with GPS units at the tree where measurements were centered. All non-nest sites were ≥ 35 m away from the nearest nest site located during the study period. Given the high detectability of cavity nests especially during the nestling period [39] and the high survival rate of white-headed woodpecker nests following wildfire [27], we assumed low likelihood of undetected active nests at non-nest sites.

Environmental data at nest and reference sites

We compiled five remotely sensed and five field-collected environmental variables for use as modeling covariates, along with additional salvage logging metrics compiled solely to inform discussion (Table 2). Remotely sensed data, compiled at a 30-m-pixel resolution, described topography, pre-fire canopy cover, burn severity, and extent of ponderosa pine-dominated forest at all wildfire locations. We also compiled salvage logging extent at Toolbox and Canyon Creek locations. Biological relevance of these variables is described by previous authors [5, 27, 34, 35]. Remotely sensed variables described either a local (single pixel or a 9-pixel [0.81-ha] neighborhood) or a landscape scale [3,409-pixel [1-km radius; 314-ha] neighborhood; approximate area likely containing a home range; 33]. We derived topographic variables from LANDFIRE [40]. Previous studies described associations with topographic slope and aspect, which can influence microclimate and consequent vegetation structure [27, 34, 35]. We quantified burn severity using data from Monitoring Trends in Burn Severity [41] and canopy cover using Gradient Nearest Neighbor (GNN) data [imagery year 2002; 42]. We used the delta normalized burn ratio index [ΔNBR, 43] to identify moderate-to-severely burned pixels [ΔNBR > 270; following 27], and we assumed pixels classified as “non-forest” to have zero pre-fire canopy cover. White-headed woodpeckers nest in canopy openings either generated by recent wildfire or present before fire [27, 34, and 35]. We expected white-headed woodpeckers to include some unburned or low-severity burned forest with closed canopies in their home ranges for foraging. We therefore modeled habitat suitability as a function of the proportion of area burned (ΔNBR > 270) or open (canopy cover < 10%) at the nest site (0.81 ha) and home range (314 ha) scales (inter-scale correlations were r = 0.46, -0.05, and 0.48 at Toolbox, Barry Point, and Canyon Creek, respectively [n = 10,000, 10,000, and 20,000 pixels, respectively]). We expected habitat suitability to relate positively with burned or open canopies at the nest-site scale while also relating negatively with burned or open canopies at the home-range scale when accounting for relationships at both scales in the same model. We assigned values to nests reflecting the year in which they were found and we averaged values across years for each non-nest point such that non-nest data reflected the average conditions available over spatial and temporal extents surveyed.

Table 2

Remotely sensed (remote) and field-collected (field) environmental variables measured at burned forest locations where habitat models were developed for nesting white-headed woodpeckers.

Variables (abbrev)	Type	Description	Modeling covariate?
Slope	remote	pixel topographic slope as % rise over run	yes
Cosine aspect (Casp)a	remote	pixel cosine-transformed (north-south) orientation of topographic slope	yes
Local-scale percent area burned or open (LocBrnOpn)	remote	Percentage of 3×3 cell (0.81 ha) neighborhood moderately to severely burned (ΔNBR > 270) or <10% pre-fire canopy cover	yes
Landscape-scale percent area burned or open (LandBrnOpn)	remote	Percentage of 1-km radius (314 ha) neighborhood moderately to severely burned (ΔNBR > 270) or <10% pre-fire canopy cover	yes
Landscape-scale percent area ponderosa pine forest (LandPIPO)	remote	Percentage of 1-km radius (314 ha) ponderosa pine forestc	yes
Local-scale extent of logging (LocLog)b	remote	Percentage of 3×3 cell (0.81 ha) neighborhood intersecting sale units for salvage logging.	no
Landscape-scale extent of logging (LandLog)b	remote	Percentage of 1-km radius (314 ha) neighborhood intersecting sale units for salvage logging.	no
Medium snag density (SngMidDens)	field	Number of medium snags (25–50 cm DBH) per ha within 50 m	yes
Large snag density (SngLrgDens)	field	Number of large snags (>50 cm DBH) per ha within 50 m	yes
Medium-to-large live tree density (TreeDens)	field	Number of medium-to-large trees (>25 cm DBH) per ha within 50 m	yes
Percent ponderosa pine (PIPO%)	field	Percentage of medium-to-large snags and trees (>25 cm DBH) that are ponderosa pine	yes
Ponderosa pine (PIPO)	field	Whether or not nest or center tree was ponderosa pine (categorical; 0 = no, 1 = yes)	yes
Logging intensity (LogIntensity)b	field	Ratio of cut stump density to density of all stumps, snags, and trees	no

aCasp = 0 wherever Slope ≤ 2%.

bOnly assessed at Toolbox and Canyon Creek locations to measure extent (LocLog, LandLog) and intensity (LogIntensity) of post-fire salvage logging. Logging variables were compiled for reference when interpreting modeling results but not used as modeling covariates. Additionally, the size distribution for cut stumps (< 1.4 m high, ≥ 25 cm top diameter), snags (dead, ≥ 1.4 m high, DBH ≥ 25 cm), and trees (alive, ≥ 1.4 m high, DBH ≥ 25 cm) were not equivalent because diameter was measured at different heights (< 1.4 m for stumps, at 1.4 m for trees and snags), so LogIntensity represents a relative index rather than an absolute measure of logging intensity.

cPonderosa pine forest was defined based on forest type classifications provided with gradient nearest-neighbor data as all pixels listed as dominated or co-dominated by ponderosa pine [42].

Field-collected variables described either characteristics of 50-m radius patches or individual nest and non-nest snags (i.e., local scale descriptors of the nest site; Table 2). The specific dimensions of sampled plots used to measure tree and snag densities varied somewhat among study locations (S1 Appendix) and were therefore rescaled to represent per hectare counts for analysis. We also recorded the size, species, and status (live versus dead) of nest and non-nest trees. Both previous research [27, 34] and data collected here indicate white-headed woodpeckers nest almost exclusively in snags with DBH ≥ 25 cm. White-headed woodpeckers can nest in dead portions of live trees, but we rarely observed this behavior at our study locations (1 nest at Barry Point). Therefore, we only considered snags with DBH ≥ 25 cm as non-nest trees (i.e., available but unused). If the center tree for a non-nest site was alive or too small (DBH < 25 cm), we randomly selected a snag ≥ 25 cm DBH located within the 50-m patch to represent the non-nest tree for that site. We excluded from analysis those non-nest points that lacked any snags ≥ 25 cm DBH within 50 m (3, 3, and 2 non-nest sites excluded at Toolbox, Canyon Creek, and Barry Point, respectively). Given these restrictions, we did not consider tree size or live/dead status as modeling covariates, although we do report DBH descriptive statistics to inform discussion. Many woodpecker species favor decayed snags for nest cavity excavation [27, 44], but we did not record decay at Canyon Creek so we did not model relationships with decay. We measured non-nest points in the field concurrently with nest site measurements. Some non-nest points were measured repeatedly in multiple years (n = 86 at Toolbox), in which case we used the mean of replicate measurements for model development.

In addition to environmental variables, we compiled metrics describing the extent and intensity of salvage logging at Toolbox and Canyon Creek at relevant spatial scales remotely and in the field (Table 2). We initially included logging covariates in models, but doing so reduced predictive performance (i.e., models discriminated nest from non-nest sites no better than random with logging covariates–area under the receiver-operating-characteristic curve [AUC] ≈ 0.5), perhaps reflecting variation in prescriptions and consequent implications of salvage logging among study locations. Regardless, we were mainly interested in informing management decisions prior to logging (e.g., designation of habitat reserves). We therefore only report descriptive statistics for logging metrics to inform inference from modeling results.

Habitat suitability models

Maxent with remotely sensed data

To support habitat mapping, we developed Maxent models with remotely sensed data to differentiate environmental conditions at used (nest) versus available sites. Maxent is informed by use-availability data [a.k.a. presence-background; 45–47] and was found effective for quantifying habitat in unburned forest [35]. We used the logistic Maxent output (0–1 range) as HSIs [see 35, 46]. Available sites informing Maxent models were 10,000 pixels for each wildfire location drawn randomly from within survey units and up to 250 m outside unit boundaries. After verifying comparable performance with more complex models, we favored relatively simple models to facilitate interpretation of habitat relationships (S2 Appendix). Accordingly, reported models only included variables with contributions of ≥ 5% gain in initial model runs [variable contributions described by 46]. Additionally, we only considered linear, quadratic, and interactive covariate effects [48].

Weighted logistic regression with remotely sensed and field-collected data

To inform management prescriptions, we developed weighted logistic regression (WLR) models informed by remotely sensed and field-collected data. We weighted non-nest sites (y = 0) and nest sites (y = 1) to negate the influence of their respective sample size on the estimated response [w = 1; w = n/n; 3, 32]. This scheme correctly treats the overall ratio of nest-to-non-nest sites as an artifact of sampling. The estimated response is thereby interpretable as a relative index of habitat suitability [HSI; 3]. To maximally inform discrimination of suitable from unsuitable habitat, zeros should represent unused sites uncontaminated with misclassified nest sites [49]. Our field methods resulted in a thorough search of study units, so we are reasonably confident that nests were never located within 30 m of non-nest sites (resolution of remotely sensed data) during the study period. We fitted weighted logistic regression models using the glm function in R [v. 3; 50]. Considering our sampling methods, we suspect WLR HSIs primarily quantified suitability for nest site selection. Because some nests were found after initiation, however, our data could additionally represent nest predation and competition, which also potentially shape white-headed woodpecker nesting distributions.

We constructed and compared candidate models with alternative covariate combinations using an information theoretic framework [51]. We constructed candidate models describing all combinations of relevant covariates limited to a maximum of 1 covariate per 10 nests rounded up (i.e., 5 covariates for n = 46 and 47 nests at each of Toolbox and Canyon Creek locations, respectively) to avoid overfitting. We only considered first-order linear covariate relationships and did not consider quadratic, interactive, or higher order effects. We compared candidate models using small-sample corrected Akaike’s Information Criterion (AICc) and AICc model weights. We first fitted models to individual study locations with sufficient nest site data to support model development (Toolbox, Canyon Creek) and retained top models (lowest AICc) for evaluating predictive performance. Variance inflation factors [see 52] for all covariates were ≤ 2.57 (i.e., R2 ≤ 0.61 when regressing a given covariate against all other covariates), so multicollinearity was not a concern. At the Toolbox location, we only measured field-collected variables at non-nest sites within the 13 largest survey units (≥ 23.3 ha), so WLR models were fitted to data from these units (33 nest and 134 non-nest sites).

Model evaluation

We assessed transferability of models developed at individual wildfire locations (Toolbox and Canyon Creek) by evaluating predictions applied at alternate locations. We measured predictive performance using AUC [53] to measure discrimination accuracy of nest from non-nest sites. An AUC = 0.5 indicates discrimination no better than random, whereas AUC = 1 indicates perfect discrimination [53]. We considered model predictions useful for discriminating nest from reference sites when the lower limit for the 95% confidence interval (CI) for AUC exceeded 0.5. We used the pROC package in R to calculate bootstrapped AUC CIs [54].

We considered transferability indicative of consistency in environmental relationships across wildfire locations, so we pooled data across locations where models were transferable to develop a final model to inform management (hereafter pooled models). We re-ran model selection and fitting procedures (see above) using covariates included in the final (Maxent) or top-ranked (WLR; within 2 AIC units) models at individual locations as candidate covariates when developing pooled models. So that pooled models would be informed equally by each individual wildfire location, we adjusted the analyzed data as follows. For the pooled Maxent model, the proportion of available (background) sites from each location was set to match the proportion of nest sites from each location. For the pooled WLR model, we down-weighted data from the location with a larger sample of nests (Canyon Creek) so that the sum of the weights for observations from each location equaled the sum of observation weights for the other location in the pooled dataset.

HSI relationships with hatched-nest densities

We related HSIs with observed densities of hatched nests (i.e., nests with at least 1 nestling), reflecting both nest site selection and a component of fitness, nest survival to hatching. HSI relationships with hatched-nest densities can inform interpretation and application of HSIs in terms relevant to forest management and population targets. Additionally, hatched nests for wildfire-associated woodpeckers are highly detectable [39], reducing the need to account for detection probability when estimating densities. We verified hatching status by monitoring nests and checking their status regularly [36]. We plotted the density of hatched nests for equal-area moving window bins [described by 29] to visualize density changes with increasing HSI. Additionally, we used HSI relationships with hatched-nest densities to identify natural breaks useful for classifying suitability classes often desired for management planning [55]. We selected two thresholds to distinguish three potential suitability classes (low, moderate, and high suitability) that clearly differed in hatched-nest densities. Two nests at each of Toolbox and Canyon Creek locations did not hatch and were therefore excluded from samples used to relate HSIs with hatched-nest densities.

We calculated 95% CIs for hatched-nest densities within suitability classes defined by HSI thresholds using bootstrapping [56]. We used 600-m resolution cells forming a grid that extended across study units as sampling units for bootstrapping. We assigned nest, non-nest, and available sites the IDs of cells containing them, and we resampled the data by cell ID with replacement to generate 5,000 bootstrapped samples (n = 57 and 169 cells for Toolbox nest–non-nest and use-availability data, respectively; n = 104 and 212 cells for Canyon Creek nest–non-nest and use-availability data, respectively). We assumed non-nest (for WLR) and available (for Maxent) sites accurately represented the proportion of area surveyed in each HSI class for estimating class-specific densities. We report as confidence limits the 2.5% and 97.5% median-unbiased quantiles for bootstrapped samples calculated with the quantile function in R (type = 8).

We provide R scripts and an R workspace with data needed to replicate all analyses and plots in this manuscript (S1 Data).

Results

Conditions at nest sites differed notably from non-nest sites at all wildfire locations (Table 3). Live tree densities (TreeDens) were consistently lower at nest compared to non-nest sites. Other notable patterns were not consistent across locations. For example, Toolbox and Canyon Creek nest sites were more severely burned or open (LocBrnOpn) at a local scale but less severely burned and less open at a landscape scale (LandBrnOpn) than non-nest sites. We did not observe this apparent scale-dependent tradeoff at Barry Point. At Barry Point, the extent of ponderosa pine-dominated forest (LandPIPO) at nest sites deviated more positively from non-nest sites than was apparent at Toolbox or Canyon Creek locations. Overall conditions available for nesting also varied among locations (see non-nest sites, Table 3). Toolbox and Canyon Creek locations were characterized by greater coverage of ponderosa-dominated forest (LandPIPO), smaller trees (DBH), and less severely burned or less open canopies at a landscape scale (LandBrnOpn) than at Barry Point. Logging at Toolbox was more intense (LogIntensity) and more extensive (LocLog, LandLog) at nest compared to non-nest sites, whereas this pattern did not hold at Canyon Creek (Table 3).

Table 3

Mean (SD) values for remotely sensed and field-collected variables for nest and non-nest sites at three wildfire study locations.

Complete variable names and descriptions are in Table 2. n = 33 and 134 for Toolbox nests and non-nests, n = 47 and 176 for Canyon Creek nests and non-nests, and n = 19 and 19 for Barry Point nests and non-nests, respectively. Units are % for Slope, number per ha for tree and snag densities (SngMidDens, SngLrgDens, TreeDens), and cm for DBH.

Variables	Toolbox		Canyon Creek		Barry Point
	nest	non-nest	nest	non-nest	nest	non-nest
Slopea	7.3(5.6)	7.8(6.6)	21.3(12.9)	23.5(11.4)	9.2(6.2)	9.1(6.6)
Caspa	0.19(0.66)	0.27(0.57)	-0.16(0.7)	-0.18(0.69)	-0.34(0.54)	-0.09(0.68)
LocBrnOpna	95.3(13)	81.6(32.4)	82(26.8)	80.4(28.9)	77.2(29.5)	73.1(33.6)
LandBrnOpna	61.1(19.7)	65.7(21.5)	60.7(14)	68.1(13.7)	69.8(7.4)	69.3(10)
LandPIPOa	74.9(7.9)	72.3(10.6)	59.8(10.1)	59.2(10.5)	51.7(5.7)	31.5(28.2)
LocLoga,e	24.9(41.9)	19.2(36.9)	13(30.1)	18.4(33.9)	0(0)	0(0)
LandLoga,e	29.6(21.2)	21.6(22.8)	13.2(11.8)	13.2(13.5)	0(0)	0(0)
SngMidDensb	65.1(39.2)	57.6(42.3)	93.6(54.2)	83.9(51.7)	63(41.8)	74.3(41.4)
SngLrgDensb	10.3(12.4)	7.9(11.8)	13.8(10.6)	13.7(12.1)	16.2(12.3)	13.6(10.4)
TreeDensb	5.3(13.5)	26.8(35.6)	27.8(57.2)	63.4(115.3)	14.2(21.6)	23.7(28.5)
PIPO%b	39(27.7)	34.3(28.2)	62.5(33.6)	57(31)	36.3(19.2)	36.3(28)
PIPOb,c	0.36	0.38	0.55	0.55	0.47	0.47
DBHb,d,e	35.7(16.9)	37.7(16.7)	47.3(19.8)	41.5(14.6)	59.2(20.4)	47.8(25.3)
LogIntensityb,e,f	0.21(0.26)	0.09(0.2)	0.09(0.17)	0.11(0.2)	0(0)	0(0)

aremotely sensed.

bfield-collected.

cCategorical variables–reported values are proportion ponderosa pine.

dDBH = diameter breast height of nest or center snag.

eDBH and logging variables are described for reference but were not used for modeling.

fLogging conditions varied through time, and values represent conditions averaged across sites and years.

Maxent models consistently retained local- and landscape-scale percent area burned or open (LocBrnOpn and LandBrnOpn) variables as primary contributors (Table 4). Maxent HSIs described positive and negative nest habitat relationships with LocBrnOpn and LandBrnOpn, respectively (Fig 2). LandPIPO also contributed to the Toolbox model and Slope to the Canyon Creek model (Table 4). At Toolbox, Maxent HSIs related positively with ponderosa-pine dominated forest, and at Canyon Creek, HSIs related negatively with topographic slope (Fig 2). These covariates represented relatively minor contributions, however, and were not retained in the pooled model (Table 4).

Table 4

Variable contributions (% gain) for Maxent models developed with remotely sensed data measured at white-headed woodpecker nest and available sites in burned forest (Oregon, USA).

Models at individual locations (Toolbox, Canyon Creek) were evaluated for transferability before pooling (Toolbox & Canyon Creek).

Variable	Toolbox	Canyon Creek	Toolbox & Canyon Creek
LocBrnOpn	55.8	38.5	53.3
LandBrnOpn	38.6	47.8	46.7
LandPIPO	5.6	--	--
Slope	--	13.7	--

Fig 2

Maxent HSI relationships with underlying covariates.

Covariates are local- and landscape-scale percent area burned or open (LocBrnOpn, LandBrnOpn), landscape-scale percent ponderosa pine-dominated forest (LandPIPO), and percent topographic slope (Slope). Complete descriptions are in Table 2. LandPIPO and Slope relationships (bottom panels) are from models developed at individual wildfire locations (Toolbox, Canyon Creek) and were not included in the final model intended to inform management (pooled model) but are reported to inform discussion.

Top-ranked WLR models described nest habitat relationships with burn severity or canopy openness (LocBrnOpn, LandBrnOpn), live tree density (TreeDens), and ponderosa pine (PIPO% or LandPIPO; Table 5). As with Maxent models, WLR HSIs related positively with LocBrnOpn and negatively with LandBrnOpn, again supporting a scale-specific tradeoff with burn severity and canopy openness (Fig 3, Table 6). WLR HSIs also related negatively with TreeDens (live tree density), additionally indicating selection for burned nest sites, and positively with PIPO% (i.e., dominance of nest sites by ponderosa pine). The top-ranked model at Canyon Creek excluded LocBrnOpn and PIPO%, indicating weaker nest habitat relationships with these variables at that location (Table 6). The negative estimated relationship with live tree density at Canyon Creek, however, suggests an affinity for locally burned or open nest sites consistent with patterns at Toolbox. The absence of PIPO% from the Canyon Creek WLR model mirrored the absence of LandPIPO from the Canyon Creek Maxent model, in contrast with Toolbox models, which consistently described positive nest habitat relationships with ponderosa pine variables.

Table 5

Model selection results for weighted logistic regression models describing nest site selection by white-headed woodpeckers in burned forest.

Models within 2 AICc units from the top-ranked (lowest AICc) model and the intercept-only model are presented. The total number of candidate models considered were 386, 638, and 64 for Toolbox, Canyon Creek, and pooled datasets, respectively. Complete lists of candidate models for each dataset are included in S1 Data. Complete covariate names and descriptions are in Table 2.

Developed at	Covariates	K	ΔAICc
Toolbox	LocBrnOpn + LandBrnOpn + TreeDens + PIPO%	5	0.0
	LocBrnOpn + LandBrnOpn + LandPIPO + TreeDens	5	0.5
	LocBrnOpn + LandBrnOpn + TreeDens	4	0.8
	LandBrnOpn + TreeDens + PIPO%	4	1.4
	Intercept-only	1	14.0
Canyon Creek	LandBrnOpn + TreeDens	3	0.0
	LandBrnOpn + TreeDens + PIPO%	4	1.1
	LocBrnOpn + LandBrnOpn + TreeDens	4	1.3
	LandBrnOpn + TreeDens + PIPO	4	2.0
	Intercept-only	1	9.3
Toolbox & Canyon Creek	LocBrnOpn + LandBrnOpn + TreeDens + PIPO%	5	0.0
	LandBrnOpn + TreeDens + PIPO%	4	0.3
	LandBrnOpn + TreeDens	3	1.2
	LandBrnOpn + LandBrnOpn + TreeDens	4	1.8
	LocBrnOpn + LandBrnOpn + LandPIPO + TreeDens + PIPO%	6	1.9
	Intercept-only	1	10.6

alowest AICc = 80.4, 123.1, and 175.0 for Toolbox, Canyon Creek, and pooled models, respectively.

Fig 3

Weighted logistic regression (WLR) HSI relationships with underlying covariates.

Covariates are local- and landscape-scale percent area burned or open (LocBrnOpn, LandBrnOpn), density of live trees (TreeDens), and percent ponderosa pine (PIPO%). Complete descriptions are in Table 2. The model represented pooled data across Toolbox and Canyon Creek wildfire locations (Oregon).

Table 6

Parameter estimates (and standard errors) for top AICc-ranked weighted logistic regression habitat suitability index (HSI) models for nesting white-headed woodpeckers in burned forest.

Models were developed with data from Toolbox, Canyon Creek, or both locations combined. Estimates and standard errors describe logit-linear relationships with HSI. Complete covariate names and descriptions are in Table 2.

Parameter	Developed at:
	Toolbox	Canyon Creek	Toolbox & Canyon Creek
Intercept	0.289 (1.661)	3.691 (1.235)	0.748 (0.987)
LocBrnOpn	0.037 (0.02)	--	0.015 (0.01)
LandBrnOpn	-0.058 (0.021)	-0.052 (0.018)	-0.037 (0.012)
TreeDens	-0.052 (0.02)	-0.008 (0.003)	-0.009 (0.005)
PIPO%	0.021 (0.012)	--	0.012 (0.006)

Models developed at each of the Toolbox and Canyon Creek locations exhibited transferability between those two locations, but not to Barry Point (Table 7). Compared to development locations, AUC scores tended to be lower at alternate locations (except Canyon Creek Maxent model applied at Toolbox). AUC CIs consistently exceeded 0.5 at Canyon Creek and Toolbox locations, suggesting models remained informative there, whereas AUCs were consistently lower with 95% CIs that overlapped 0.5 at Barry Point. This pattern was consistent regardless of model type and data used for model development (i.e., Maxent informed by remotely sensed data versus WLR informed by remotely sensed and field-collected data). We therefore excluded Barry Point data from final pooled models (described in Tables 4, 5, 6, 7 and 8, and Figs 2 and 3).

Table 7

AUC scores (with bootstrapped 95% CIs) indicating discrimination accuracy of nest from non-nest sites for white-headed woodpecker in burned forest.

Models were developed at Toolbox and Canyon Creek wildfire locations, and evaluated at both development locations and the Barry Point location. Maxent models were developed with remotely sensed data, and weighted logistic regression models with both remotely sensed and field collected data. AUCs with 95% CIs overlapping 0.5 indicated poor discrimination accuracy.

Model type	Applied at:	Developed at:
		Toolbox	Canyon Creek	Toolbox & Canyon Creek
Maxent	Toolbox	0.76(0.68,0.85)	0.72(0.62,0.81)a	0.72(0.63,0.81)
	Canyon Creek	0.61(0.52,0.7)a	0.64(0.54,0.73)	0.62(0.53,0.71)
	Barry Point	0.56(0.37,0.76)a	0.53(0.34,0.72)a	0.57(0.38,0.75)a
WLR	Toolbox	0.81(0.74,0.89)	0.62(0.52,0.72)a	0.76(0.67,0.85)
	Canyon Creek	0.66(0.57,0.75)a	0.71(0.62,0.79)	0.69(0.61,0.78)
	Barry Point	0.57(0.38,0.75)a	0.55(0.36,0.74)a	0.57(0.38,0.76)a

aAUC scores outside where models were developed are of particular interest for assessing limitations to predictive performance and model transferability.

Table 8

Density of hatched nests in suitability classes defined by HSI thresholds based on Maxent and weighted logistic regression (WLR) models (Maxent thresholds = 0.34, 0.6; WLR thresholds = 0.3, 0.53).

Models were developed with data on nesting white-headed woodpeckers from Toolbox and Canyon Creek burned forest locations (Oregon). 95% CLs (values in parentheses) are bootstrapped with 600 m cells as sampling units. Percent nests is the expected percent of hatched nests assuming equal area sampling across suitability classes. Area surveyed was calculated as the proportion of reference sites (available for Maxent, non-nest for WLR) in each suitability class multiplied by the total area surveyed at each location.

Model	Location	Quantity	Habitat suitability (HSI) class
			Low	Moderate	High
Maxent (remotely sensed)	Toolbox	Density	0.07 (0.01,0.13)	0.38 (0.22,0.54)	0.98 (0.48,1.54)
		Percent nests	5 (1,10)	26 (16,43)	69 (50,80)
		Area surveyed (ha)	7,119.4	6,379.9	1,530
	Canyon Creek	Density	0.16 (0.06,0.3)	0.77 (0.49,1.06)	1.51 (0.67,2.5)
		Percent nests	7 (2,14)	31 (19,50)	62 (41,76)
		Area surveyed (ha)	4,902.5	3,510.2	661
WLR (remotely sensed & field collected)	Toolbox	Density	0 (0,0)	0.14 (0.06,0.26)	0.73 (0.37,1.34)
		Percent nests	0 (0,0)	16 (7,32)	84 (68,93)
		Area surveyed (ha)	2,188	7,019.8	3,008.5
	Canyon Creek	Density	0.19 (0.04,0.43)	0.29 (0.14,0.5)	1.02 (0.68,1.49)
		Percent nests	13 (3,26)	19 (9,33)	68 (52,82)
		Area surveyed (ha)	2,113.8	4,124.4	2,835.5

Hatched-nest densities differed along HSI gradients and among suitability classes for pooled models at Canyon Creek and Toolbox locations (Table 8, Fig 4). Based on densities for moving-window bins, we identified Maxent HSI thresholds of 0.34 and 0.6 and WLR HSI thresholds of 0.3 and 0.53 for classifying suitability. Resulting categories of low, moderate, and high suitability habitat contained distinct hatched-nest densities, although for WLR HSI densities primarily differed in high suitability habitat compared to low and moderate (Fig 4). At Canyon Creek, hatched-nest densities were higher overall and differences among suitability classes were less pronounced than at Toolbox. Nevertheless, hatched-nest densities consistently increased from low to moderate and from moderate to high suitability classes at both locations (Table 8).

Fig 4

Densities of hatched nests for white-headed woodpeckers along habitat suitability index (HSI) gradients in burned forests.

Maxent HSIs quantify relationships with remotely sensed environmental variables only, whereas weighted logistic regression (WLR) HSIs also quantify relationships with field-collected variables. Low, moderate, and high suitability classes are differentiated by two HSI thresholds selected at natural breaks in densities for equal-area moving window bins (small circles) and in the distribution of nest site HSIs (rug bars). Large circles and error bars are density estimates and bootstrapped 95% CIs, respectively, for habitat suitability classes.

Discussion

We found limited transferability of HSI models for nesting white-headed woodpecker in burned forests. Accordingly, we met our objectives within a range of conditions represented by Toolbox and Canyon Creek locations where models effectively predicted nesting distributions (indicating consistency in habitat relationships). We therefore expect models provided here to be informative for managing post-fire forests within but not necessarily outside this range of conditions (e.g., not at Barry Point). Both Maxent and WLR models showed similar transferability, suggesting both can be informative, the former for mapping suitable habitat to inform conservation planning and the latter to inform post-fire silviculture prescriptions. Hatched-nest densities can facilitate interpretation of HSIs and HSI-based suitability classes and evaluate implications of alternative management scenarios or prescriptions for nesting populations.

The conditions most consistently identified as suitable by models here were canopy mosaics or edges, wherein nest placement favored burned or open-canopy sites adjacent to less-burned and relatively closed-canopy sites. In burned and unburned forests, white-headed woodpeckers generally favor relatively open canopies for nest placement within home ranges that include some closed-canopy forests thought to provide foraging habitat [27, 34, 35]. Modeled relationships with LocBrnOpn (positive), TreeDens (negative), and LandBrnOpn (negative) were consistent with this general pattern. Models also described positive relationships with ponderosa pine at various scales (LandPIPO, PIPO%) and a negative relationship with topographic slope, which are consistent with current knowledge [27, 33–35] but were less consistent across study locations. Descriptive statistics for Barry Point sites were also consistent with some of these relationships (e.g., see values for LandPIPO and TreeDens; Table 3). Nevertheless, the combination of covariate relationships quantified at Toolbox, Canyon Creek, or both locations did not readily discriminate nest from non-nest sites at Barry Point. Taken together, these results suggest this suite of features can be informative for quantifying nesting habitat in burned forests with some generality, but not everywhere.

Previously, Wightman et al. [27] developed a Mahalanobis D2 model [57] using nest sites from the Toolbox Fire in central Oregon to map habitat suitability for nesting white-headed woodpeckers. Their model relied on remotely sensed metrics of burn severity, pre-fire canopy cover, and the interspersion-juxtaposition of different forest patches. These metrics were ecologically relevant, but independent data from other wildfires were not available for evaluating predictive accuracy [27]. Our study represents a refinement of Wightman et al.’s [27] work analogous to those made for white-headed woodpecker nest habitat models implemented in unburned forests [35]. Additionally, the size and density of snags and trees are not well represented by remotely sensed data, so including field measurements adds important information for quantifying nesting habitat relevant to management (e.g., salvage logging) prescriptions.

Limitations to model transferability

Differences in habitat availability and consequent nest site selection likely caused limited transferability of models to Barry Point from other wildfire locations. Although forests at the three study locations all represented lower elevation dry conifer forests, forest coverage and composition varied among locations. Ponderosa pine-dominated forest was least extensive at Barry Point, and forest patches were interspersed more with non-forest openings composed primarily of sagebrush (Artemisia tridentata), mountain mahogany (Cercocarpus ledifolius), and juniper (Juniperus occidentalis). These open-canopy sites were present prior to wildfire, so assuming availability of snags suitable for nesting at these sites, white-headed woodpeckers at Barry Point may not have depended as heavily on wildfire to generate canopy openings desirable for nesting. Ponderosa pine-dominated forest was less extensive at Barry Point and nearly 40% of nests were located in juniper trees situated in open-canopied forests (n = 19 nests). Relatively large ponderosa pine (DBH ≥ 25 cm) provide nesting and foraging substrates, especially high quality foraging resources [e.g., 58]. In contrast with their counterparts at Toolbox and Canyon Creek, white-headed woodpeckers at Barry Point may have focused selection less towards canopy mosaics and instead towards ponderosa pine-dominated forests, where they likely found trees desirable for foraging. Nesting relationships with size and configuration of forest patches and canopy openings and comparison of such metrics across wildfire locations could help evaluate these potential explanations for our results.

Even at Toolbox and Canyon Creek locations, we observed differences that could impose limits on model applicability and generality. Toolbox sites were characterized by more extensive coverage of ponderosa pine-dominated forest and less topographic slope than at Canyon Creek. These differences may reflect variation in selectivity for these features between wildfire locations. Models may need to allow relationships with slope and percent ponderosa pine to be modulated by habitat availability to correctly inform predictions [sensu 23].

Salvage logging could also influence model transferability. During preliminary analyses, salvage logging covariates reduced predictive performance (AUC ≈ 0.5). This poor predictive performance did not necessarily indicate a lack of relationships with salvage logging but rather that such relationships were too inconsistent to reliably inform prediction across study locations. Descriptive statistics did in fact suggest somewhat contradictory relationships with logging at Canyon Creek versus Toolbox (Table 3). We therefore excluded salvage logging covariates from models here to maintain focus on developing predictive models. Studies specifically examining salvage logging effects could complement predictive habitat models to inform forest management. Selective logging may sometimes improve habitat suitability by creating canopy openings desirable for nest placement, but logging effects will likely vary among wildfire locations with different logging prescriptions. Data collected over a range of logging prescriptions and pre-logging environmental conditions are needed to quantify generally applicable relationships with logging. Salvage logging may alter interpretation of variables based on remotely sensed pre-fire canopy data, potentially necessitating greater reliance on field-collected data in heavily logged areas. Salvage logging levels (extent and intensity) represented at our study locations did not compromise the value of remotely sensed data for characterizing nesting habitat and predicting nesting distributions for white-headed woodpeckers.

Model transferability can vary with modeling technique and data quality [59-61]. Previous study shows improvements to transferability when including field-collected data [32]. Here, WLR models not only included field-collected data, but were also developed with use–non-use (nest–non-nest) data, which are generally expected to provide higher quality information than data without non-use (i.e., absence) data [15, 49]. Nevertheless, we found comparable transferability with Maxent models informed only by remotely sensed and use-availability (i.e., presence-background) data. Factors such as modeling technique or sample size may compensate somewhat (but probably not entirely) for reduced information quality where field-collected and non-use data are unavailable.

Following our primary objective, we took an approach often represented in machine learning studies wherein we exhaustively considered potential combinations of candidate covariates and evaluated predictive performance to verify the utility of the resulting model [see also 59–63]. Selection from a narrower set of candidate models representing a priori hypotheses [described in 51] may be more appropriate for research investigating mechanisms underlying observed habitat relationships, which would complement and inform development of predictive models.

Model application guidelines

We suggest using the pooled Maxent model to map habitat to inform selection of habitat reserves for white-headed woodpeckers and/or salvage logging units following wildfire, whereas the pooled WLR model (along with descriptive statistics of field-collected data) provides finer resolution information relevant to designing management prescriptions. We expect most applications will require categorization of habitat (e.g., as low, moderate, or high suitability). Hatched-nest densities in relation to HSI categories can facilitate their application to inform management and compare alternative management scenarios to meet particular population targets. Management plans could aim to maximize retention of moderate and high suitability habitats classified by the pooled Maxent model. Silviculture prescriptions could target conditions associated with high suitability habitat classified by the WLR model. Conditions within a 1-km radius neighborhood of nest sites informed models, so buffering habitat reserves and treatments would be needed to provide sufficient foraging habitat and maintain nest habitat suitability as described by these models. We developed a toolset to apply HSI models for disturbance-associated woodpeckers (including models presented here) within a GIS framework, along with a manual demonstrating potential applications [64].

Models provided here do not comprehensively quantify all habitat features required for nesting. Given the potential importance of ponderosa pine-dominated forest and topographic slope suggested at individual wildfire locations, we suggest restricting Maxent HSI application to a range of conditions corresponding with where we surveyed (i.e., 1-km radius neighborhood coverage of ponderosa pine-dominated forest [LandPIPO] ≥ 40% and Slope ≤ 40%). Descriptive statistics here (Table 3) combined with other studies [27, 33] suggest logging prescriptions that retain relatively large decayed snags would benefit nesting white-headed woodpeckers (Table 3). Although models suggest local snag densities were less important than other habitat features for selecting nest sites, intensive salvage logging could reduce habitat suitability by limiting snag-related resources. Experimental study examining population response to a range of logging prescriptions could complement HSI models for informing post-fire forest management. Finally, habitat selection does not always optimize fitness [65, 66], so habitat-fitness relationships would complement HSI models to inform habitat management [e.g., 27, 34].

Towards more predictive models

Studying mechanisms underlying observed habitat relationships would further inform predictive modeling. Ponderosa pine trees provide multiple foraging opportunities (cones provide seeds and invertebrates; and bark, needles, and pine sap provide insects) and desirable substrate for nest cavity excavation [33, 58, 67–69]. The association of white-headed woodpeckers with canopy mosaics represents a more recent discovery and is not fully understood. Canopy openings generated by wildfire could provide refuge from nest predators [e.g., red squirrel [Tamiasciurus hudsonicus]; [70] and opportunities for aerial insectivory [5, 44, 71]. In contrast, adjacent unburned closed-canopy forests are thought to provide critical opportunities for foraging on live ponderosa pine trees. Following wildfire, white-headed woodpeckers could also find foraging opportunities in high densities of recently burned snags. These hypotheses are largely untested, and their importance has implications on the level, scale, and character of canopy mosaics that optimize habitat suitability, as well as behavioral plasticity in the use of mosaic habitats. Improved understanding of resources provided by canopy mosaics would further inform how to quantify mosaics in predictive models. Additional tree-level data could help refine models that include field-measured covariates to inform management prescriptions (e.g., nesting use of juniper trees and metrics of snag decay). Following previous work and our understanding of underlying mechanisms, we chose to estimate the expected association with canopy mosaics by estimating relationships at different scales within the same model [22]. Future research could also consider quadratic relationships with canopy cover and burn severity as an alternative or additional approach for quantifying these relationships.

Contemporary best practices include model averaging to account for model-selection uncertainty when generating model-based predictions [72]. Practitioners could average across WLRs presented here to infer potential management effects on habitat suitability. For transparency and interpretability towards informing the design of management plans and prescriptions, however, we opted to select a single best model. Although our selected model represents the best balance of information and parsimony given available data, our conception of which covariates are necessary and sufficient for prediction could evolve with additional sampling and study of underlying mechanisms. Nevertheless, we expect to retain major habitat components of canopy mosaics and ponderosa pine even with further model refinements [e.g., 35].

Broader implications

Management of dry conifer forests is currently focused on restoring and maintaining forest conditions with which white-headed woodpeckers are closely associated and that have been disrupted by human activities [27, 33, 34, 35]. Because of their association with these conditions, white-headed woodpeckers have now been adopted as a focal species for assessing the effect and efficacy of forest management treatments and strategies [e.g., 73, 74]. Some evidence suggests burned forests may represent essential habitat for white-headed woodpecker population persistence [27, 34]. The species consequently draws particular attention from managers seeking to balance socioeconomic demands for timber and public safety with habitat conservation when planning salvage logging. Models can generally inform post-fire forest management that targets habitat for white-headed woodpeckers in the East Cascades and Blue Mountains (northwestern U.S.A.), but additional data are needed in other portions of the species range (e.g., Modoc Plateau, represented here by Barry Point, and North Cascades).

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4 Feb 2020

PONE-D-19-34065

Development and evaluation of habitat suitability models for nesting white-headed woodpecker in burned forest

PLOS ONE

Dear Dr. Latif,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

This paper provides an important contribution to the challenge of balancing the needs of native species, such as the white-headed woodpecker, and forest management objectives.  As both of the reviewers point out, the paper is well written but could be improved by some revisions.  Many of the suggestions will increase the utility of the paper and provide additional desirable details.  I will highlight a few of these but I encourage you to read through the reviewers comments carefully as they make very excellent suggestions for ways to improve the manuscript.

One key aspect of this study is the development of HIS models for woodpecker nesting habitat following fire management applied to several novel locations (e.g., transferability).  As the results suggest, it is critical to evaluate whether models can be applied more generally or are highly dependent on local context.  This is a strength of the paper that is not highlighted as well as it could be.  For example, there is no direct comparison of habitat suitability with only remote sensing data only versus with only field-collected data, although only remote sensing data is compared to the combined field and remote sensing data. This omission makes it challenging to assess the value of the data at different scales.  The white-headed woodpecker seems like an excellent model to test this but there may need to be some additional information provided about their ecology to better frame this discussion as Reviewer 1 points out.

I agree with both of the reviewers that the analyses are thorough and, for the most part, well described.  However, there are a few issues highlighted by both reviewers worth noting.  In particular, there are clearly far more models that you describe than are listed in the paper.  It would be very valuable for the reader to be able to evaluate the larger set of candidate models.  As reviewer 2 points out, there is a revised understanding of AIC in the literature that would encourage going beyond the models within 2 AICc units of the top model.  It would also be valuable to provide additional information in Table 6 where you compare the top set of models for each location (e.g., Akaike weights).  Reviewer 2 points out that descriptive statistics are mentioned but not described or displayed.  Some other details are mentioned about salvage logging and I agree with reviewer 1 that if that is to be a focus of the paper than more details are needed in both the methods and the results to provide the support for the discussion.  Otherwise, this aspect may need to be de-emphasized.  Both reviewers provide detailed suggestions on the figures and tables that would strengthen the paper (e.g., combining Tables 2 and 3).  Also, more detail is needed in your description of the models, their parameters, and the assumptions for each approach (e.g., reviewer 1 comments specifically on weighted linear regression, reviewer 2 makes suggestions about model evaluation).  Additionally, a different set of reference sites are used for each of the models.  It is important to explain why these changes are made and what potential implications they have on the results.  I agree with reviewer 1 that the hatched-nest analysis is not well described, which undermines its purported value.  Understandably there are a lot of these details that may need to be added to a supplement but they would strengthen the usability of your approach by others.

The goal of the study is to inform post-fire forest management by identifying suitable habitat for fire-associate species.  You mention the evaluation of management scenarios but this is not demonstrated in the results unless you count the different sites as different scenarios; it would be very valuable to see some example scenarios modeled.  In addition, to explore the issue of transferability the models could be refined with inclusion of a measure of habitat availability, as you provide this a possible explanation for the differences that you found.  Reviewer 1 makes some very constructive suggestions to improve the discussion and better tie the paper together and reviewer 2 highlights some of the elements that need clarification.

Overall, this paper will be a strong contribution to the literature but it needs some revision.  The paper does a very nice job of highlighting two different approaches to modeling habitat suitability while highlighting some of their strengths and weaknesses.  The conclusions are important and seem supported by the data, although some improvement in the presentation will strengthen this connection.

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Reviewer #1: Excellent and well-written paper. Thanks for the opportunity to review it. This paper will add greatly to our knowledge of white-headed woodpecker use of post-fire landscapes. It will also be useful for forest managers who are faced with increasing fire severity and frequency in the northwestern U.S., where this species is of conservation concern. As the authors point out, managers in these areas are tasked with difficult decisions – salvage logging is done to meet timber targets but can be detrimental to this and other at-risk cavity nesters. Most of my comments were minor or relating to semantics – as well as trying to improve the readability for individuals not familiar with white-headed woodpecker nesting ecology. I commend the authors on a great manuscript and hope this will be published soon, so it can be used by managers.

My biggest concern is that the paper starts out with an emphasis on salvage logging, but in the results and discussion the salvage log results are glossed over because they did not improve the predictive value of the model. To fix this, the authors could re-write the abstract and introduction to remove the focus on salvage logging. Managers need information on salvage logging however, so I’d prefer instead that the authors provide some of the models that did include salvage logging, and/or do more with the descriptive statistics on salvage logging. At the very least, the authors could start the discussion with a paragraph that describes the effects of salvage logging on this species. Even if the paragraph simply states/clarifies that the levels of salvage logging examined in this study had no effect on habitat suitability for white-headed woodpecker.

Specific comments:

Line 61 – suggest changing wording to “managers must strive to identify suitable habitat….”

Line 72 – suggest removing “project”

Line 85-86 – many things can cause geographic variation in model applicability. Suggest adding the following to the beginning of this sentence “Many factors can cause geographic variation in model applicability, however, such as biotic interactions, local adaptation and behavior rules….”

Line 98-99 – soften “require”; suggest replacing with the word “use”, or something similar; not enough is known of this species for such strong language, plus it does not necessarily account for variation in habitat use range-wide

Line 98 – sentence is confusing because it starts out that “white-headed woodpeckers nest in….unburned forested landscapes….. maintained by mixed severity fire”. Do you mean to imply that historically the unburned forests were maintained by mixed severity fire? Otherwise unburned forests being maintained by mixed severity fire seems incongruous. Also note in southern portion of this species range conditions appear different – white-headed woodpecker may not require areas maintained by mixed severity fire in southern CA, for example. Too little research has been done in such locales to be sure either way.

Line 101 – suggest removing “critical”

Line 103 – after ponderosa pine, add “in the northern portion of their range”

Line 104 – remove “suggesting possible source-sink dynamics” or add a sentence to clarify. As written, it is confusing to the reader.

Line 108 – Use of “further” here seems out-of-place. Suggest deleting.

Line 110 – the objectives 1 and 3 are difficult to understand as written. From reading the paper, objective 1 seems to be to develop models of nesting habitat suitability using GIS covariates and field covariates at 3 fires that had some level of salvage logging. Objective 2 is understandable as written. As written, objective 3 seems to be the same as objective 1.

Line 113 – what is meant by the phrase “considering our success in achieving these objectives”? Suggest deleting and start the sentence with “We also evaluated our ability to quantify….”

Table 1 – I appreciate the detailed info in this table, as well as the detailed comments indicated by subscripts.

Line 153 – Use of “affected” is confusing. Suggest stating instead that “Portions of the toolbox and canyon creek fires were salvage logged.” Or clarify early on in this paragraph what is meant by “affected”.

Line 153 – Photos of different fires/study areas – even black-and-white – would be nice to add for the reader.

Line 195 – 35 m is apparently the minimum distance What was the mean and range of distance the non-nest measurements were from the nests? See comment relating to line 300.

Table 2 – Is LandPIPO pre-fire live or post-fire live ponderosa pine?

Line 243 – 25 cm dbh does not seem large to me. Also, in Table 3 large snags are those >50 cm. Suggest deleting the word “large” and simply state that white-headed woodpeckers nest mostly in snags >= 25 cm. I suggest this change be implemented throughout the document. Avoid vague qualifiers “small” or “large” and use numbers (e.g., snags 25-25 cm, > 50 cm, etc).

Table 3, also line 380 – Decay is so vague given the guidelines (yes/no whether ‘nest or center tree showing signs of decay’), plus it wasn’t recorded at one site, so I think it should be removed from the document. It will only confuse the results plus the authors do a nice job on line 252 describing why decay was not modeled. Remove it from the document and simply state that measuring decay is difficult and we did not measure it in this study.

Table 3 – It might be nice to merge tables 2 and 3 so the reader has all the model covariates in one table. I also suggest separating out the covariates that were not included in models. Right now they are indicated with small subscripts. You could have two subheadings: (1) measured covariates that were included in models, and (2) measured covariates that were not included in models.

Line 300 – The weighted logistic model assumes use/nonuse data, in other words? (e.g., Nad’o and Kanuch 2018. Plos one 13:e0200742; rather than use/availability data, like Maxent..) Perhaps this is discussed in detail later, but further consideration of the violations of this assumption are needed here, especially given this is a territorial species and ‘non-use’ sites were apparently as close as 35 m to nests (line 195), which is within an area likely defended by territorial pairs (given that white-headed woodpecker inter-nest/nearest neighbor distances in other studies are typically >100 m). If this species is territorial around nests, it seems it would have been better to buffer around nests before drawing a sample of random points to be used in a use/nonuse design. What if one white-headed woodpecker had a nest in a ‘suitable’ habitat pixel, but it was surrounded by say 2-5 ha of other suitable pixels. Those 2-5 ha of suitable pixels could not have been used by another nesting white-headed woodpecker because of territoriality, and thus may have been incorrectly classified as unsuitable habitat in this design; this may bias the HSIs. Temporal aspects could also be considered – a pair may have used one of the unused pixels the year after you finished the study, even though the suitability for nesting did not change among years. It seems a use/availability SDM is better over all for this study (which is true of most wildlife studies, really). If WLRs are kept in the study to enable analysis of the field-collected variables, please be clear in the text here that you may have violated some assumptions – and be transparent about those assumptions so readers less familiar with SDMs can understand that those results may be a bit more questionable.

Line 303 – I get what the authors are trying to say with this sentence (WLR HSIs primarily quantified relative suitability…) but this argument would need a fair amount of justification – seems more than the scope of this paper. Please consider deleting this sentence.

Line 328 – by “informative”, do you mean transferable?

Line 337 – Why was the proportion of available sites was set to match the proportion of nest sites for the pooled maxent model?

Line 342, and throughout – Especially here in this section describing pooling of study sites, the word ‘location’ gets confusing – just because it has so many meanings. Can the authors use the word “study area” or ’study site’ or ‘fire complex’ consistently throughout the manuscript (and in this section) instead of the word location.

Line 343 – I do not understand this sentence, and thus I do not understand what the ‘hatched’ nests are being used to validate. This paragraph is difficult to follow. (line 343-350) After reading the results it became clear to me that the hatched nests are being used to identify thresholds for low, moderate, and high suitability but I think that has limited value and I suggest deleting the thresholds from the manuscript. See comment for line 481.

Table 4. It is nice to have a table showing the mean values for each covariate.

Line 404 - This statement is unclear to me “supporting a scale-specific tradeoff with burn severity and canopy openness”. Suggest deleting it here, and moving any pertinent argument for or against this concept to the discussion.

Line 462 – Could the authors also present a table with sensitivity and specificity so readers can see in what direction these models performed best (I mean, were the models better at predicting true positives or true negatives?).

Tables 7 and 8. Write out the fire names in the column headings. There are enough acronyms in this table that the reader has to look up without abbreviating the fire names too.

Table 8 - Similarly, suggest removing RS and RS&FC from the first column. Those items are described in the table heading, as well as in the methods, and make the column more confusing than it needs to be. It might be ideal to separate out AUC values for the models transferred to other locations (I mean place those with the subscript “a” in a different table, or in a subheading of this table).

Line 481 – Building off my comment associated with line 343, I do not see the value of the “hatched-nest” analysis. I do think in the methods line 343 the authors could do a better job describing what this analysis is aimed to accomplish. It seems to be used to establish thresholds, but why are thresholds needed? Thresholds are tricky, and are not needed for applying habitat models. They can be quite sensitive – I mean that small changes in the value of thresholds can lead to large changes in the amount of area classified as suitable. Moreover, there are more established ways of assigning thresholds from SDMs like Maxent. I think this analysis should be dropped, and the suitability of habitat from the models be assessed based on the numerical value of the HSIs at given locations. If the authors do choose to keep this analysis, it may help to add it as an objective to the introduction, and please make the methods around line 343 more understandable.

Line 534 – This is well-written.

Line 556 – The species requires snags when breeding so this statement would only hold true if there were snags in the open sites at Barry Point - before the fire.

Line 560 – similar to previous comments, I’d remove the qualifier ‘large’ (and small!) as much as possible. It only adds to confusion among managers about how to provide habitat for this species, which research has shown nests in areas with heavy timber production – thus relatively ‘small’ ponderosa pine trees can also provide nesting and foraging substrates. Best to just use numbers, rather than vague verbiage like large and small.

Line 569 – Use of ‘modulate’ is unclear here.

Line 611 – Poor word choice with ‘favor’. I think the authors mean to imply that prescriptions that protect large decayed snags would benefit white-headed woodpecker. The use of the word favor here at first made me think the authors were suggesting prescriptions should harvest large snags.

Line 616 – This is well written.

Line 625 – How does this sentence relate to white-headed woodpecker? For one thing, nest predators are largely unknown for this species and there is no point in perpetuating theories that are not well-supported by data. Second, the literature indicates that aerial insectivory is not a common foraging method for this species.

General comment – the word mosaic seems a bit overused and is not common parlance. My main reason for commenting is it may confuse readers. Could the authors use the word ‘patchy’?

Line 620 – in general, this section does not add much to the paper. I suggest deleting it.

General comment for the discussion – Two paragraphs would help tie this paper together more nicely: (1) First, start the discussion with a paragraph on the effects of salvage logging, because that is how the abstract starts (and salvage logging is mentioned early in the introduction also). Readers who want to skip the methods and results could then zoom down to the discussion, and the first paragraph would then inform them of the overall effects of salvage logging on this woodpecker species. Even if salvage logging did not impact the habitat suitability, it would still be valuable to start the discussion with a statement to that effect, along with a brief review of the salvage log prescription that were analyzed in this study. (2) add a management implications section and describe implications of results pertaining to salvage logging.

Reviewer #2: The authors have submitted a well-written manuscript that reports on the use of Maxent to make predictions about habitat suitability for White-headed Woodpeckers at burns in Oregon, USA. The basic approach was to compare nests vs non-nest sites at three burns. Two of the sites appeared to have better predictive ability but the third site differed, making any transferability inappropriate.

I really liked the manuscript and appreciate the depth of analyses that went into the patterns reported in the manuscript. Coupled with the extensive field data, this manuscript represents a lot of effort! My comments are mainly editorial in nature.

The main issue I have is with the dumbing down of quantitative analyses. Rather than telling the reader that previous analyses didn’t show any difference so we only present the simplified version, the authors should provide all of the information and let the reader decide for themselves. Likewise, if the authors are going to discuss analyses that were conducted, they need to present those analyses. And, finally, if the authors are going to rank candidate models, show the reader ALL of the models rathe than filtering it down to just the delta AICc < 2. I find this particularly annoying.

Here are more specific comments on this issue:

130 More details need to be provided on this “preliminary analysis”. What is meant by “substantially different relationships”?

288-290 Is this statement about verifying comparable performance with more complex models documented anywhere? The reference to citation 35 pertains to a 2015 paper comparing nest use HSIs, with presumably an entirely different database. I think this information should be included in an appendix.

311-312 Is this statement about only using first-order linear covariate relationships related to the previous statement about using simpler models? As before, this information should be provided in a supplement / appendix.

366 I did not have access to S2 data so was unable to evaluate or provide feedback. Likewise, at line 851, the authors indicate there is a zipped folder with a git repository. None of this was available when evaluating this manuscript.

414 The authors compare the global to a reduced subset of models. I thought the authors previously said they did not use more complex models. Please clarify. At the very least, the reader needs to know what models were in the global models vs the reduced models if the authors are going to reference global vs reduced in Table 5.

439 The authors present only those candidate models within 2 AICc units from the top model. The full suite of models should be provided in a supplement / appendix. The reader would be interested in knowing how many models were withing 2-3 AICc units. Was there a clear break or was there a continuum of supported models that extended beyond 2 units? This dumbing down of the data presentation can be particularly annoying to readers that want to see the full suite of candidate models.

452 Most modern day information theorists recommend abandoning the delta < 2 mantra. See extensive discussion of this by Burnham et al. (2011). They advocate against that arbitrary cutoff. My recommendation to the authors is to adopt a more modern approach where any of the models with AICc<10 are considered. The obvious solution would be to use model-averaging instead of only relying on the <2 models.

Here is what Burnham et al. (2011) write:

Δ>2 Rule. Some of the early literature suggested that models were poor (relative to the best model), and might be dismissed if they had Δ>2. This arbitrary cutoff rule is now known to be poor, in general. Models where Δ is in the 2–7 range have some support and should rarely be dismissed. Inference can be better based on the model likelihoods, probabilities, and evidence ratios and, in general, based on all the models in the set. From these quantitative measures one can then assign their own value judgment if they wish.

Burnham, K. P., D. R. Anderson, and K. P. Huyvaert. 2011. AIC model selection and multimodel inference in behavioral ecology: Some background, observations, and comparisons. Behavioral Ecology and Sociobiology 65:23-35.

573 Like I have mentioned previously, details about analyses used need to be documented. What are these “descriptive statistics” and where can they be found? Similarly, lines 610-611 discuss “descriptive statistics” about “logging prescriptions” favoring large decayed snags.

Line Edits

20 Insert scientific name for the woodpeckers

35 AUC is not defined; likewise it is not defined in the main text (line 275) at first mention. Instead, it is defined all the way down at 325.

36 Add two decimals to 57.00 so format matches 0.53

90 Define the term “transferability”

127 Insert “(hereafter Canyon Creek Fire;”

134 The sc name was already introduced at line 103.

135 The authors are inconsistent on whether they introduce e.g. or i.e. within parentheses or with merely a comma. This problem occurs throughout.

137 All numbers in the thousands should have a comma for consistency. The authors arbitrarily include the comma or not. See 1,603; 4,347; 4,727; and subscript e for example in Table 1. See also line 358 among other places.

165 Should be “prior to”

168 This is the first mention of DBH so it should be “diameter at breast height (DBH) > 23 cm per hectare”. The authors introduce the abbreviation before the definition.

204 Add extra hyphen “30-m-pixel”

218 The authors need to provide a citation for the statement about the woodpeckers nesting in canopy openings.

266 Typo “diamter”

327 The statement that AUC=1 indicates perfect discrimination needs a citation.

328 This line is the first occurrence of “confidence interval” so it should be abbreviated here (not later in the ms at line 354 as it is currently formatted).

344 This is the first introduction of “hatched nests” so the “(i.e. nests with at least 1 nestling)” information should appear here, not on line 347.

346 The authors indicate that by using hatched nests, detection probability was nearly perfect. How does this approach account for nests that failed before hatching? Does this not bias towards habitat with successful nests (e.g. those areas with less predators, unsuitable nest trees, etc).

352 Two nests were excluded plus any other nests that went undetected, of course.

414 This is the first time the abbreviations TB and CC have been used. They need to be defined before the abbreviation can be introduced like this in the table.

456 At some point, the authors will want to clean up their tables so that the numbers are aligned by decimal point. I appreciate that they may not have done this for the submitted version of their manuscript.

470 Remove hyphen in bootstrapped so it matches the style used throughout the ms.

559 Unclear whether this 40% figure comes from the literature or is based on unpublished data. Either way, the authors need to provide a citation (if published) or a sample size that this percentage is based on if this is unpublished data.

570 Change “correct” to “correctly”

581 Unclear what levels are being referenced here. Levels of what?

594 Are the authors speaking more generally here or are they specifically referring to WHWOs when they mention “habitat reserves”?

598 Insert hyphen “hatched-nest densities”

600 Is this objective of reaching “particular population targets” in play? If so, a citation and / or more background information should be provided here.

610 Unclear what this 40% number represents. How is “dominated or co-dominated by ponderosa pine” defined? Does one just count up all of the trees within a 1-km radius and calculate what proportion of trees are PP? If so, how does one define co-dominated? Some folks are not as up on forestry lingo and need a bit of help understanding the terminology.

617 Are the authors advocating for habitat-fitness data as a prerequisite for constructing HSI models, or just that it would be nice to have? Ambiguous as worded.

641 Citation needed for the statement about restoring and maintaining forests and the disruption by humans.

648 These geographic terms (e.g. East Cascades, Blue Mountains, Modoc Plateau, North Cascades) will mean nothing to a casual reader. Please provide geographic reference to put in context. Oregon? USA?

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Reviewer #1: No

Reviewer #2: No

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Submitted filename: review2.docx

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20 Mar 2020

We have responded to all reviewer and editor comments on the content of our manuscript in the document entitled "Response to Reviewers" uploaded with this submission.

Submitted filename: ResponseToReview_PlosOne_Feb2020.docx

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15 Apr 2020

PONE-D-19-34065R1

Development and evaluation of habitat suitability models for nesting white-headed woodpecker (Dryobates albolarvatus) in burned forest

PLOS ONE

Dear Dr. Latif,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

This paper provides an important contribution to the challenge of balancing the needs of native species, such as the white-headed woodpecker, and forest management objectives and needs only minor revisions.  I appreciate your thorough attention to the suggestions and questions of the initial reviewers.  As a result of these changes, the paper is much stronger, better written and provides more compelling conclusions.  The revised methods have improved clarity and better highlight the important aspects of the approach utilized.  I appreciate the revision of the analysis to address issues mentioned by the reviewers and the results now better support the conclusions. The discussion provides an excellent overview of the results in a broader context and makes valuable suggestions on future research.  Reviewer #2 has some minor suggestions that you should address in your revisions.  Please, note, though, that Reviewer #3 has highlighted some concerns about the analytical methods leading to their decision to reject.  You will certainly need to address the issue of quadratic effects and provide clarification about why that might not be appropriate or feasible for these data and/or the application intended.  While I agree that it might be worthwhile to include some additional landscape analyses to further explore configuration effects, there are a seemingly endless number of variables you could include in HSI models.  However, the suggested analyses (e.g., fragstats) do not seem necessary if the potential limitations in the conclusions you can make with the current analysis are explicitly acknowledged in the discussion and you think these additions are beyond the scope of the study.  Overall, this paper will make a strong contribution to the field with some additional minor revisions.

==============================

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: (No Response)

Reviewer #3: (No Response)

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #2: Yes

Reviewer #3: Partly

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

Reviewer #3: No

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Reviewer #2: Yes

Reviewer #3: Yes

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Reviewer #2: Yes

Reviewer #3: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #2: I was the proverbial reviewer 2 in the previous version of this manuscript. I have read over the new version of the manuscript and reviewed all of the line-by-line responses to my previous comments. As I said previously, this is a great manuscript and well written. The authors have done a great job revising the manuscript. I thank them for their thorough treatment of the reviewer comments. Well done!

Only a couple of minor remaining edits:

85 Change “Due to” to “Because of”. Due to modifies a noun, it is incorrect to use it to modify a verb.

164 The authors might consider using “autumn” instead of “fall”. The latter term is only used in North America.

172 Redundant “diameter at breast height (DBH)” with previous line.

360 Inconsistent missing comma in 5,000

368 Should this be “S3 Appendix” to match the terminology used for S1 and S2, previously? See also line 441.

503 Insert hyphen “field-collected”

506 You need a “respectively” after the statement about large circles are density estimates and error bars are 95% CIs.

Reviewer #3: The authors have a well-written paper about a timely subject. The choice of topics and the broad experimental design seem appropriate to answer their research questions. A red flag I noticed in the methods is that the authors didn’t consider quadratic effects. Considering burn intensity and tree density likely have some optimum values which are neither 0 nor 100%. It seems like there is a strong a priori justification for examining quadratic effects. This choice absolutely needs to be justified. For example white-headed woodpeckers have a negative relationship with tree density, but clearly it cannot have a maximum at 0, as there would be no trees for nesting.

A second red flag is that you argue landscape configuration is likely interacting with forest characteristics to influence results lines 550-587. Why not use fragstats or some other approach to quantifying landscape configuration and incorporate these characteristics among the sites into the modeling approach?

I was thinking about these puzzling methodological choices so I ran supplied example code. The modeling used was more appropriate for an exploratory data analysis, but seems like a pretty flagrant abuse of data dredging best practices. Considering the obvious ignoring of appropriate a priori hypotheses, and instead building gigantic linear combinations of model covariates via a data dredging approach, the authors may benefit from reexamining the methodological tactics employed here.

**********

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Reviewer #2: No

Reviewer #3: No

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23 Apr 2020

Our responses to reviewers are detailed in an attached Word document.

Submitted filename: ResponseToReview_PlosOne_Apr2020.docx

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28 Apr 2020

Development and evaluation of habitat suitability models for nesting white-headed woodpecker (Dryobates albolarvatus) in burned forest

PONE-D-19-34065R2

Dear Dr. Latif,

We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements.

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Karen Root, Ph.D.

Academic Editor

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Additional Editor Comments (optional):

Thank you for the careful attention to all of the suggestions and questions.  The changes you have made enhance the paper providing better balance and clarity, and it is now suitable for publication.  Your paper provides an important addition to our understanding of modeling disturbance effects on vulnerable species.

Reviewers' comments:

1 May 2020

PONE-D-19-34065R2

Development and evaluation of habitat suitability models for nesting white-headed woodpecker (Dryobates albolarvatus) in burned forest

Dear Dr. Latif:

I am pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please notify them about your upcoming paper at this point, to enable them to help maximize its impact. If they will be preparing press materials for this manuscript, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

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on behalf of

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PLOS ONE