Birds that dive may be at greater risk of extinction

Birds that dive underwater — such as penguins, loons and grebes — may be more likely to go extinct than their nondiving kin, a new study finds.

Many water birds have evolved highly specialized bodies and behaviors that facilitate diving. Now, an analysis of the evolutionary history of more than 700 water bird species shows that once a bird group gains the ability to dive, the change is irreversible. That inflexibility could help explain why diving birds have an elevated extinction rate compared with nondiving birds, researchers report in the Dec. 21 Proceedings of the Royal Society B.

“There are substantial morphological adaptations for diving,” says Catherine Sheard, an evolutionary biologist at the University of Bristol in England, who was not involved with the study. For instance, birds that plunge into the…