Reproductive success of a generalist brood parasite predicts the rate of parasitism in the subsequent year

Brown-headed cowbirds (Molothrus ater) rely solely on hosts to raise their young. Although cowbirds parasitize 200+ species, recent evidence suggests that females avoid unsuitable hosts that either reject parasitic eggs or provide incompatible parental care. Female cowbirds may be able to improve their own reproductive success with information pertaining to the fledging success of cowbird or host offspring. This, in turn, could influence the laying decisions and host choices of cowbirds in subsequent years. To determine whether host reproductive success and/or cowbird reproductive success in the previous year affect the likelihood of cowbird parasitism, we examined nesting data for a highly suitable host, the prothonotary warbler (Protonotaria citrea). We recorded parasitism status (yes or no), number of cowbird eggs, and the number of host and cowbird fledglings for 3848 warbler nests from 1994-2010 in southern Illinois. Data were analyzed using a generalized linear mixed model (GLMM) with binomial distribution. We accounted for variation in site, nest box, identity of female warbler, and year in our analysis as random effects and included month and the parasitism rate in the previous year as covariates. From one year to the next, the probability of parasitism for a given site increased with cowbird reproductive success and tended to decrease with prothonotary warbler reproductive success even after controlling for the ambient rate of parasitism in the previous breeding season. This is the first study to suggest that the fledging success of cowbirds increases future host use by female cowbirds.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2013

Author dc:creator

• Albores, Amber

Contributors dc:contributor

• Hoover, Jeffrey P.
• Schelsky, Wendy

• brown-headed cowbird
• brood parasitism
• reproductive success
• host selection
• prothonotary warbler

Statement dc:rights

• Copyright 2013 Amber Albores

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/45323

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/45323