Reduced compensatory growth capacity in mistimed broods of a migratory passerine.

Phenotypic plasticity has recently been proposed to increase population viability when rapid anthropogenic environmental changes cannot be tracked by means of evolution. This assumes that environmental changes do not constrain phenotypic plasticity itself, which has rarely been examined in natural populations. In areas of climate warming, many long-distance migratory birds breed increasingly late relative to the period of peak food supply, and the temporal mismatch may constrain plastic life-history traits such as nestling growth. We combined 23 years of food availability and breeding data with a 3-year experimental manipulation of nestling growth trajectories in a Central European population of collared flycatchers (Ficedula albicollis) to examine the potential impact of climate-related mistimed breeding on nestling developmental plasticity. Timing of the food peak was predicted by winter climate, and the median hatching date of broods was earlier in springs with earlier food peaks. However, the adjustment of hatching date was incomplete and the population largely missed the food peak in years with very early food peaks. After imposing a temporary, experimental food shortage on nestlings, the extent of compensatory growth in body mass differed among years, and this difference was apparently related to the distance of hatching dates from the yearly food peak. Growth compensation declined with distance from the peak. These results suggest that mistimed phenology may not only create permanently adverse conditions for migratory species but it may also constrain the plastic responses of individuals to temporary disturbances. Therefore, climate change may not only favour but also restrict phenotypic plasticity.