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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?

Two male cowbirds
Two male cowbirds.


November 18, 2019


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