Is brood parasitism related to host nestling diet and nutrition?

Abstract

ABSTRACT Food and nutrient limitation can have negative effects on survival, fecundity, and lifetime fitness of individuals, which can ultimately limit populations. Changes in trophic dynamics and diet patterns, affected by anthropogenic environmental and landscape change, are poorly understood yet may play an important role in population regulation. We determined diets of Wood Thrushes (Hylocichla mustelina), a Neotropical migratory songbird species sensitive to urbanization, and explored how brood parasitism by Brown-headed Cowbirds (Molothrus ater) may be related to Wood Thrush nestling diets. Effects of brood parasitism on host nestling diets is an understudied stressor that may help explain observed population declines. We measured carbon (δ13C) and nitrogen (δ15N) stable isotopes of 7 invertebrate food sources (snails, spiders, isopods, earthworms, myriapods, insects, and caterpillars), blood plasma from adult male and female Wood Thrushes and from Wood Thrush nestlings in nests with and without Bro...