Neotropical winter habitat of the Magnolia Warbler: Effects on molt, energetic condition, migration timing, and hematozoan infection during spring migration

Abstract

Events in one season can have carryover effects on birds in a subsequent season. Little research has addressed how conditions where a bird winters influence it during migration. We investigated such carryover effects on Magnolia Warblers (Dendroica magnolia) captured during spring migration in northwestern Ohio. We examined signatures of stable carbon isotopes (δ13C) in feathers grown in the neotropics where the birds winter and hypothesized that drier habitats (as indicated by δ13C) would advance infection by avian hematozoa, delay migration, and depress energetic condition and extent of prealternate molt. The range of δ13C in feathers (-25.0% to -19.9%) was similar to that published for tissues grown in winter by other nearctic-neotropical migrant songbirds, suggesting that the Magnolia Warblers we captured wintered over a range of xeric to mesic habitats. Nonetheless, we detected no significant relationships between habitat moisture (as indicated by δ13C in feathers) and spring migration timing (capture date), energetic condition at capture, number of molted wing coverts, or extent of black breast streaking in these Magnolia Warblers. furthermore, we found no consistent relationships between δ13C in feathers and rates of hematozoan infection. Our data suggest that for the Magnolia Warbler, habitat moisture may not be the primary factor affecting the quality of the winter habitat or that in this species there may be no carryover effects in spring migration. © The Cooper Ornithological Society 2010.