Last season, as I approached one of my 70-plus nest boxes in mid-spring, nothing seemed out of the ordinary. The standard-style-rectangular box I was checking was one of a number I maintain in the Southwest Michigan Land Conservancy's 3 Chipman Preserve in Eastern Kalamazoo county. This parcel has been undergoing consistent land restoration from a former tree nursery back to the savannah prairie which is the remnant dominate habitat.
The female Easter Bluebird that exited the box prior to my arrival went about her calling from a nearby birch tree. There was no sign of the male, as often is the case, since he might be away gathering prey for himself or for offering to his mate sitting in the box. (The female was by that time incubating the eggs, as I shortly ascertained). When I opened the nest box for inspection, all seemed normal as well.It was when I was checking the five new eggs for a temperature that I caught a glimpse of some bright blue in the nest. At first I supposed it was a random feather brought in to feather the nest, as it were. I'm an inquisitive steward, though, so I pulled the whole nest out--to photograph the eggs in the nest--and also to satisfy my curiosity. It was then that I was startled by the truth of the matter.
Built into the very weave of the nest was the dried-out body of an adult male Eastern Bluebird. I'd found dead adult birds in the bottom of a box or on the top of some portion of a nest before- most often after a winter of sub-zero temperatures or after observing territorial disputes between House Wrens and Bluebirds, or Tree Swallows. But never had I seen one so plainly, immaculately utilized in the nest construct.
I can only speculate upon the scenario behind the demise of the this adult and the order of the nest building. The nest appears half-finished where the body was built into it. As for the reasons it was built into the nest, an assumption or two can be allowed. Perhaps after losing a fight with a House wren, the dead male could not be physically extracted from the almost-completed nest by his mated female, and so she continued her work. She certainly may have been fertilized already and was due to lay, and in addition possible possessed a strong and singular nest-site fidelity to this box.
After the loss of a mate, many birds will either find a new mate- or continue on alone in brooding and raising the young. In this particular case, I never saw another male at the box, yet that doesn't preclude that the female hadn't re-mated and that he was then simply out of my sight. In any case, all five of the eggs hatched, and all of the nestlings fledged right on schedule.
(c)2009 Michigan Bluebird Society
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