Migration strategies of wintering populations of red knots Calidris canutus rufa in South America: the role of parasite pressure

D'AMICO, V.; BERTELLOTTI, M.; BAKER, A.; TELLINO JUNIOR, W.; GONZÁLEZ, P.

ARDEOLA

SEO/Birdlife

Lugar: Madrid, España; Año: 2008 vol. 55 p. 193 - 202

0570-7358

SUMMARY.—Migration strategies of wintering populations of red knots Calidris canutus rufa in South America: the role of parasite pressure. Aims:To test whether different migratory strategies in red knots (Calidris canutus rufa) are a response to spatial variation in parasite pressure at different marine wintering sites as predicted by the ‘parasite’hypothesis of Piersma (1997). Location: Río Grande and Tierra del Fuego, Argentina; Maranhão, Brazil; Delaware Bay, USA. Methods: The abundance of ectoparasites and blood parasites and the frequency of parasitized birds were estimated at the three sites. Ectoparasites were scored visually and parasites in blood were searched for with molecular assays and observations of smears on slides. Birds caught in mixed flocks refueling in Delaware Bay were assigned to either northern (Maranhão or possibly Florida) or southern wintering sites (Tierra del Fuego) using stable isotopes in feathers. Results: All ectoparasites found were feather lice were Mallophaga, Phthiraptera. The 4.4 % of birds in Tierra del Fuego and the 100 % in Maranhão had ectoparasites. In Delaware Bay the proportion of parasitized birds from northern and southern sites was not significantly different. No blood parasites (Plasmodium spp., Haemoproteus spp. and Leucocytozoon spp.) were found in the samples. Conclusions: Only 4.4 % of birds wintering in Tierra del Fuego had ectoparasites whereas all birds wintering in Maranhão were parasitized, often heavily. During migration through Delaware Bay in May, the proportion of parasitized birds from northern (50 %) and southern (40.1 %) sites was not significantly different, indicating that many southern birds had been infected during a short stopover on the northwards migration or by direct contact in Delaware Bay. The parasite hypothesis predicts that red knots should evolve migrations to low-parasite marine wintering sites to reduce the fitness consequences of high ectoparasite load in tropical Maranhão, but there is likely to be a tradeoff with increased mortality for longdistance migration to cold-temperate Tierra del Fuego. All blood parasite assays were negative for Plasmodium spp., Haemoproteus spp. and Leucocytozoon spp, consistent with the low incidence of blood