Mismatched begging displays between foreign and host offspring reduce brood parasite fitness

TitleMismatched begging displays between foreign and host offspring reduce brood parasite fitness
Publication TypeJournal Article
Year of Publication2014
AuthorsRivers, JW, Blundell, MA, Rothstein, SI
JournalBehavioral Ecology
Pagination785 - 793
Accession NumberKNZ001760
KeywordsAgelaius phoeniceus, begging, Bell’s vireo, brood parasitism, brown-headed cowbird, Molothrus ater, provisioning behavior, red-winged blackbird, Vireo bellii

Obligate brood parasites must obtain food from unrelated host parents during the developmental period, and this may be especially difficult when parasitic nestlings are raised alone. Unlike specialist brood parasites, generalist brood parasites use a single begging display for a range of host species. In this study, we 1) tested whether the begging display of the generalist brown-headed cowbird (Molothrus ater) was more exaggerated than the closely related, nonparasitic red-winged blackbird (Agelaius phoeniceus) and 2) examined how begging displays were linked to food provisioning when both foreign species were raised by the Bell’s vireo (Vireo bellii), a small cowbird host. We also quantified parental provisioning to unparasitized broods containing 1–4 vireo nestlings to provide a reference provisioning curve to provide context for assessing the feeding rate to foreign offspring. We found blackbirds begged as intensely as (or more intensely than) cowbird nestlings, vireo parents provisioned both species similarly, and the amount of food provisioned to unparasitized broods increased with brood size and maintained per-capita vireo growth. However, feeding of a single foreign nestling was significantly less than that of a modal brood of 4 vireos, indicating parents fed foreign nestlings at submaximal rates. Vireos did not respond to begging of foreign nestlings in the same manner as their own offspring, and this led to significant fitness costs for foreign nestlings. We conclude that a single foreign nestling provided an inadequate stimulus for vireos, probably because of a mismatch between the begging displays of foreign and host offspring.