Cowbirds change their eggs' sex ratio based on breeding time

(University of Illinois at Urbana-Champaign, News Bureau) 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.
Source: EurekAlert! - Social and Behavioral Science - Category: International Medicine & Public Health Source Type: news