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Photo © Keith Williams
Photo © Christine Boran

NestWatcher Spots Odd Eggs

Christine Boran of Virginia shared this photo from a nest box on the Woolwine House Bluebird Trail. Something has caused three of the four Eastern Bluebird eggs to be malformed, the most extreme of which is bean-shaped. At the time of writing, 2 eggs had hatched, but only 1 nestling survives (now 10 days old on August 23rd, 2018).

In her 13 years of nest monitoring, Christine says she has never seen anything like this before. We sought the opinion of Dr. Mark Hauber, author of The Book of Eggs: A Life-Size Guide to the Eggs of Six Hundred of the World’s Bird Species, about what could have caused this. Dr. Hauber told us, “It looks like the female laid the eggs too fast without the shell being fully formed—I would suspect that these eggs are incredibly thin. They are incredible eggs indeed!” Bluebirds typically lay one egg per day, so in this case “too fast” is relative to the 24-hour laying interval.

Christine is closely watching this nest, and she invites interested NestWatchers to follow along on the trail’s Facebook page.

Cornell Lab of Ornithology

Cornell Lab of Ornithology