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Referential alarm calls increase vigilance in brood parasite hosts

October 6, 2021

Yellow warblers are hosts to brood parasitic brown-headed cowbirds, which rely on other species to raise their offspring. Warblers use referential “seet” calls to warn female warblers specifically of the brood parasitic brown-headed cowbirds that may try to lay eggs in their nests. When exposed to experimental playbacks of seet calls one day, female warblers were more vigilant the next morning, researchers report in the current issue of the journal Biology Letters.


October 6, 2021


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In times of ecological uncertainty, brood parasites hedge their bets

August 21, 2020

Some birds lay their eggs in the nests of other bird species and let the host parents raise their young. A new study finds that in times of environmental flux, these brood parasites "diversify their portfolios," minimizing the risks of their unorthodox lifestyle by increasing the number and variety of hosts they select as adoptive parents.


August 21, 2020


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Cowbirds change their eggs’ sex ratio based on breeding time

June 25, 2020

Brown-headed cowbirds show a bias in the sex ratio of their offspring depending on the time of the breeding season, researchers report in a new study. More female than male offspring hatch early in the breeding season in May, and more male hatchlings emerge in July.

Cowbirds are brood parasites: They lay their eggs in the nests of other birds and let those birds raise their young. Prothonotary warblers are a common host of cowbirds.


June 25, 2020


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Signature call in cowbirds is the password that unlocks song learning

November 18, 2019

They say it takes a village to raise a child. But if you are a cowbird, left by your parents to be hatched and raised in the nest of unwitting foster parents, how do you know who your village is? If the signature behaviors of your bird identity are not instinctive, how do you know who to learn them from?


November 18, 2019


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