Variation in nest composition and abundances of ectoparasites between nests in colonially breeding Common Eiders Somateria mollissima

Abstract

ABSTRACTCapsule: The occurrence of high numbers of ectoparasites in nests of Common Eiders may be related to nest densities and nesting behaviour.Aims: To estimate abundances of ectoparasites and occurrence of blood-covered eggs, and relate those to nest bowl ages, nest bottom material and the incubation stages of eggs, in nests at two different Common Eider colonies.Methods: Nests were collected at Hvallátur and Rif, two sites at Breiðafjörður, West Iceland, in June and July 2012. The nest bottom material was classified to vegetation species and invertebrates were identified to species when possible.Results: The flea Ceratophyllus garei was the dominant ectoparasite at both sites, with median abundances higher at Hvallátur than at Rif in June. In July, the mean abundance of fleas was higher than observed in June at Rif. There were positive relationships between the flea abundances and the incubation stages of the nests, the blood cover of the eggs and the type of nesting material. No relationship was observed between the age of nesting bowls and adult flea abundances.Conclusion: Disadvantages of large parasite loads on the later nesters (second clutch in each nest) at Rif may be compensated by shared nest attendance and the concurrent added time for preening for females while other females attend their nests.