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Multiple parasitism of the Red-winged Blackbird: Further experimental evidence of evolutionary lag in a common host of the Brown- headed Cowbird


Ward, D; Lindholm, A K; Smith, J N M (1996). Multiple parasitism of the Red-winged Blackbird: Further experimental evidence of evolutionary lag in a common host of the Brown- headed Cowbird. The Auk, 113(2):408-413.

Abstract

We testedw hether a common host of the brood parasitic Brown-headed Cowbird (Molothruast ater),the Red-winged Blackbird (Agelaius phoeniceus),accepts cowbird eggs in its nest because the blackbird does not recognize foreign eggs(evolutionary-lag hypothesis)or because the cost of rejecting eggs or deserting the nest and re-laying exceeds the benefits of egg rejection (evolutionary-equilibrium hypothesis). We reasoned that, if egg acceptance is due to the high cost of rejection, increasing the cost of acceptance should cause the blackbirds to attempt to reject cowbird eggs, or desert the nest and renest elsewhere. We increased the cost of acceptance by adding one, two or three cowbird eggs to Red-winged Blackbird nests, and by removing one host egg for every cowbird egg added. We found no rejection at any level of parasitism. Additionally, we found that Red-winged Blackbirds incubated parasitized clutches that contained none of their own eggs. We conclude that evolutionary lag is the reason for egg acceptance in Red-winged Blackbirds.

Abstract

We testedw hether a common host of the brood parasitic Brown-headed Cowbird (Molothruast ater),the Red-winged Blackbird (Agelaius phoeniceus),accepts cowbird eggs in its nest because the blackbird does not recognize foreign eggs(evolutionary-lag hypothesis)or because the cost of rejecting eggs or deserting the nest and re-laying exceeds the benefits of egg rejection (evolutionary-equilibrium hypothesis). We reasoned that, if egg acceptance is due to the high cost of rejection, increasing the cost of acceptance should cause the blackbirds to attempt to reject cowbird eggs, or desert the nest and renest elsewhere. We increased the cost of acceptance by adding one, two or three cowbird eggs to Red-winged Blackbird nests, and by removing one host egg for every cowbird egg added. We found no rejection at any level of parasitism. Additionally, we found that Red-winged Blackbirds incubated parasitized clutches that contained none of their own eggs. We conclude that evolutionary lag is the reason for egg acceptance in Red-winged Blackbirds.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:1996
Deposited On:11 Feb 2008 12:15
Last Modified:20 Feb 2018 08:45
Publisher:American Ornithologists' Union
ISSN:0004-8038
OA Status:Closed
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.2307/4088907
Related URLs:http://elibrary.unm.edu/sora/Auk/v113n02/index.php

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