The Parasite Fauna of the Gyrfalcon (Falco rusticolus) in Iceland.

We examined 46 Gyrfalcon (Falco rusticolus) carcasses from Iceland for parasites, including 29 first-year birds and 17 second-year birds and older. Endoparasites observed were the trematodes Cryptocotyle lingua (prevalence 8%), Cryptocotyle concavum (4%), and Strigea sp. (8%); the cestode Mesocestoides sp. (27%); and the nematodes Eucoleus contortus (76%) and Serratospiculum guttatum (7%). Ectoparasites included the astigmatan mite Dubininia accipitrina (47%), a mesostigmatan rhynonyssid mite (4%), the tick Ixodes caledonicus (20%), the mallophagans Degeeriella rufa (90%) and Nosopon lucidum (7%), the flea Ceratophyllus vagabundus (7%), and the louse fly Ornithomya chloropus (7%). Cryptocotyle lingua, C. concavum, S. guttatum, D. accipitrina, I. caledonicus, and N. lucidum are new host records. Of the five most common parasites (prevalence ≥ 20%) only Mesocestoides sp. showed a significant age relationship, being more prevalent in adult falcons (P = 0.021). Eucoleus contortus was also more prevalent in adults with marginal statistical significance (P = 0.058). Frounce, caused by E. contortus (possibly also by Trichomonas gallinae, which was not searched for in the survey) was highly prevalent (43%), but did not show a relationship with host age (P = 0.210). Birds with frounce were in poorer body condition than healthy birds (P = 0.015).