On May 29th, 2019, history was made at the Cabot Head Research Station when we banded our first ever Eastern Bluebirds! Yes, bluebirds, plural. We captured one adult male and one adult female in the same net at the same time. As we were banding other birds in the banding lab, from which we have a partial view to the first two nets, we could see a somewhat large and bluish bird in a net, while an Eastern Bluebird was perched on a small birch stump nearby. That bird suddenly took off and flew towards said net. I didn’t get my hopes up, given that Eastern Bluebirds, while a relatively common bird at Cabot Head, have never been caught. So, it was quite a wonderful surprise when, after the following net check, I pulled a female Bluebird out of the bag! And an even greater surprise when the male followed. Scriber, who checked the nets and brought back the birds, didn’t say a word, to leave the surprise complete!
Both birds were adults, with almost the same wing chord, but the female was almost 2g heavier than the male: it is likely that she had an egg inside. The female showed the start of a Brood Patch, while the male has a pronounced Cloacal Protuberance (see Notes below). Both are clear indication that the birds are breeding or, at least, attempting to. Given the behaviour of the male around the net where the female was caught, we can also reasonably think that they are a pair.
After quickly taking a few pictures of this historical and memorable event, we safely released them, wishing them good luck in their breeding endeavour.
Female (left) and male (right) Eastern Bluebirds, the first and second, and so far, only bluebirds ever banded at Cabot Head!
A brood patch is a patch of featherless skin that is visible on the underside of birds during the nesting season. This patch of skin is well supplied with blood vessels at the surface making it possible for the birds to transfer heat to their eggs when incubating.
In male passerines, the accumulation of sperm in the sperm reserves causes the cloaca to become enlarged, forming the cloacal protuberance.