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Frequent vocalizing is negatively associated with brood parasitism in a host of the brown-headed cowbird

The Condor

By:
,
DOI: 10.1525/cond.2012.110006

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Abstract

Brood parasitism by the Brown-headed Cowbird (Molothrus ater) can substantially affect host species' reproductive success. The "host-activity" hypothesis suggests that parasites eavesdrop on conspicuous behaviors to locate and parasitize hosts, and several studies of cowbird hosts support this hypothesis. In contrast, a recent study of the Least Bell's Vireo (Vireo bellii pusillus) reported a negative association between the host's vocalization rate near the nest and brood parasitism. This contradictory pattern is intriguing because Bell's Vireo is a common cowbird host and vocalizes near and on its nests. We tested a key assumption of the host-activity hypothesis in a different subspecies (V. b. arizonae) to determine whether the contradictory pattern reported in V. b. pusillus is an anomaly or could be generalized to other subspecies. Unparasitized vireos vocalized more frequently than parasitized birds, confirming that the pattern in Bell's Vireos is the opposite of that reported for other cowbird hosts. Nesting stage played a role: unparasitized birds vocalized more than parasitized birds only during the nest-building and incubation stages. Given that vocalization rate and other behaviors change through the breeding season, future tests of the host-activity hypothesis should control for nesting stage. Moreover, future efforts to identify the underlying cause for the association between vocalization rate and probability of parasitism should consider the possibility of reciprocal causal relationships between them. We propose five additional hypotheses to explain why in Bell's Vireo the pattern between these two traits is opposite of what has been reported in other birds.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Frequent vocalizing is negatively associated with brood parasitism in a host of the brown-headed cowbird
Series title:
The Condor
DOI:
10.1525/cond.2012.110006
Volume
114
Issue:
1
Year Published:
2012
Language:
English
Publisher:
Cooper Ornithological Society
Publisher location:
Waco, TX
Contributing office(s):
Arizona Cooperative Fish and Wildlife Research Unit
Description:
8 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
The Condor
First page:
219
Last page:
226