Prey Selection by Swainson's Warblers on the Breeding Grounds

Abstract

Abstract. Swainson's Warbler (Limnothlypis swainsonii) breeds in bottomland hardwood forests across the southeastern United States, where it is believed to be one of the rarest breeding songbirds. Although information on its nest-site habitat is considerable, little is known about its foraging habitat except that the species is insectivorous, with a large bill used to flip fallen leaves on the forest floor. We captured Swainson's Warblers and flushed their crops to determine their diet and sampled leaf-litter arthropods and vegetation at each location of capture. We compared the proportion of arthropod orders in the crop samples to the proportion of arthropods collected in the leaf litter to determine the warbler's prey in proportion to its availability. Although Acari (mites and ticks) and Chilopoda (centipedes) were the most abundant arthropods in the leaf-litter samples (51% and 18%, respectively), these orders rarely occurred in the warblers' crops. Conversely, Araneae (spiders) and Coleoptera (beetle...