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Photo © Keith Williams
Photo © Gerald Clark

New Scientific Paper Published

It started as a curious observation: NestWatcher Gerald Clark noticed an oddly large egg among the clutch of four in the bluebird box he was monitoring last summer near his home in State College, Pennsylvania. When he went back to check the nest box in early July, there were five bluebird chicks—including two smaller-sized nestlings, which presumably came from the same egg. In other words, twins. Twinning is very rare in the bird world (fewer than half of 1% of waterfowl eggs in one study contained twins), but it’s never been observed in bluebirds before.

Clark’s find was so notable it was written up and published in the scientific journal PeerJ, in a paper co-authored by Clark and NestWatch project leader Robyn Bailey. The paper is available online, and Robyn will share more details about the story at the Bluebird Society of Pennsylvania Conference on March 29 in State College.

Cornell Lab of Ornithology

Cornell Lab of Ornithology