Brood parasitism, reproductive success, and survival in Yellow Warblers

Understanding mechanisms responsible for population declines of migratory birds requires knowledge of factors limiting population growth at all stages of the annual cycle. Interspecific brood parasites are known to have negative, short-term impacts on the reproductive success of their hosts and could have longer-term costs that reduce survival. I used an information theoretic approach to examine the age-specific costs of brood parasitism in Yellow Warblers (Dendroica petechia), a common host of Brown-headed Cowbirds (Molothrus ater) in Revelstoke, British Columbia. Age did not mitigate the costs of brood parasitism that influenced each stage of the nesting cycle and reduced annual productivity. However, there was little evidence that brood parasitism influenced the survival of yearling or older Warblers. Adult survival was influenced by climate patterns, El Niño/La Niña, that influence conditions during spring migration, demonstrating the importance of this phase of the life-cycle for population dynamics of Neotropical migrants.