title: Hampered performance of migratory swans: intra- and inter-seasonal effects of avian influenza virus.
abstract: The extent to which animal migrations shape parasite transmission networks is critically dependent on a migrant's ability to tolerate infection and migrate successfully. Yet, sub-lethal effects of parasites can be intensified through periods of increased physiological stress. Long-distance migrants may, therefore, be especially susceptible to negative effects of parasitic infection. Although a handful of studies have investigated the short-term, transmission-relevant behaviors of wild birds infected with low-pathogenic avian influenza viruses (LPAIV), the ecological consequences of LPAIV for the hosts themselves remain largely unknown. Here, we assessed the potential effects of naturally-acquired LPAIV infections in Bewick's swans, a long-distance migratory species that experiences relatively low incidence of LPAIV infection during early winter. We monitored both foraging and movement behavior in the winter of infection, as well as subsequent breeding behavior and inter-annual resighting probability over 3 years. Incorporating data on infection history we hypothesized that any effects would be most apparent in naïve individuals experiencing their first LPAIV infection. Indeed, significant effects of infection were only seen in birds that were infected but lacked antibodies indicative of prior infection. Swans that were infected but had survived a previous infection were indistinguishable from uninfected birds in each of the ecological performance metrics. Despite showing reduced foraging rates, individuals in the naïve-infected category had similar accumulated body stores to re-infected and uninfected individuals prior to departure on spring migration, possibly as a result of having higher scaled mass at the time of infection. And yet individuals in the naïve-infected category were unlikely to be resighted 1 year after infection, with 6 out of 7 individuals that never resighted again compared to 20 out of 63 uninfected individuals and 5 out of 12 individuals in the re-infected category. Collectively, our findings indicate that acute and superficially harmless infection with LPAIV may have indirect effects on individual performance and recruitment in migratory Bewick's swans. Our results also highlight the potential for infection history to play an important role in shaping ecological constraints throughout the annual cycle.
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, Geelong, Victoria, Australia hoye.bethany@gmail.com.
authors.forename: Bethany J
authors.initials: BJ
authors.lastname: Hoye
authors.affiliation: Department of Virosciences, Erasmus Medical Centre, Rotterdam, The Netherlands Laboratory of Virology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana, USA.
authors.forename: Vincent J
authors.initials: VJ
authors.lastname: Munster
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
authors.forename: Naomi
authors.initials: N
authors.lastname: Huig
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
authors.forename: Peter
authors.initials: P
authors.lastname: de Vries
authors.affiliation: SOVON Texel, Dutch Center for Field Ornithology, Den Burg (Texel), The Netherlands.
authors.forename: Kees
authors.initials: K
authors.lastname: Oosterbeek
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
authors.forename: Wim
authors.initials: W
authors.lastname: Tijsen
authors.affiliation: Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, Geelong, Victoria, Australia Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), Wageningen, The Netherlands.
authors.forename: Marcel
authors.initials: M
authors.lastname: Klaassen
authors.affiliation: Department of Virosciences, Erasmus Medical Centre, Rotterdam, The Netherlands.
authors.forename: Ron A M
authors.initials: RA
authors.lastname: Fouchier
authors.affiliation: Department of Coastal Systems, NIOZ Royal Netherlands Institute for Sea Research, and Utrecht University, Den Burg (Texel), The Netherlands.
authors.forename: Jan A
authors.initials: JA
authors.lastname: van Gils
mesh_terms: D025041:Animal Migration; D000818:Animals; D046090:Anseriformes / Q000502:physiology; D005260:Female; D009980:Influenza A virus / Q000502:physiology*; D005585:Influenza in Birds / Q000276:immunology / Q000821:virology*; D008297:Male; D009426:Netherlands; D012621:Seasons