title: Migratory common blackbirds have lower innate immune function during autumn migration than resident conspecifics.
abstract: Animals need a well-functioning immune system to protect themselves against pathogens. The immune system, however, is costly and resource trade-offs with other demands exist. For migratory animals several (not mutually exclusive) hypotheses exist. First, migrants reduce immune function to be able to allocate resources to migration. Second, migrants boost immune function to cope with more and/or novel pathogens encountered during migration. Third, migrants reallocate resources within the immune system. We tested these hypotheses by comparing baseline immune function in resident and migratory common blackbirds (Turdus merula), both caught during the autumn migration season on the island of Helgoland, Germany. Indices of baseline innate immune function (microbial killing capacity and haptoglobin-like activity) were lower in migrants than in residents. There was no difference between the groups in total immunoglobulins, a measure of baseline acquired immune function. Our study on a short-distance avian migrant supports the hypothesis that innate immune function is compromised during migration.
authors.affiliation: Institute of Avian Research, An der Vogelwarte 21, Wilhelmshaven 26386, Germany cas.eikenaar@ifv-vogelwarte.de.
authors.forename: Cas
authors.identifier: http://orcid.org/0000-0003-1049-8036
authors.initials: C
authors.lastname: Eikenaar
authors.affiliation: Department of Biology, Lund University, Ecology Building, Lund 223 62, Sweden.
authors.forename: Arne
authors.initials: A
authors.lastname: Hegemann
mesh_terms: D025041:Animal Migration; D000818:Animals; D005260:Female; D005858:Germany; D007113:Immunity, Innate; D008297:Male; D012621:Seasons; D020308:Songbirds / Q000276:immunology / Q000502:physiology*
keywords: eco-immunology; immunity; migrant; resident; trade-off