It’s mid-June and, like clockwork, I found a lady songbird today who looks to have been involved in some post-breeding dispersal. This one was a Painted Bunting, an ASY-female with a brood patch at the southeastern alcove.
At this weird building that is the Noble Research Center, I don’t find many local birds dead at the glass. There are no feeders, for example. It’s also not a spot that attracts a lot of baby birds. No, here it’s pretty obvious that migrants are the source of the great majority of the 30–40 victims here each year, with big peaks in mortality during October and May. There is another, smaller peak, however.
That third peak is “June”. For some reason, after the collisions of the northbound migrants have died down by the end of May, birds start showing up again in mid-June. These include migrants as well as local breeders like chickadees and titmice. What’s more, it’s common for these individuals to be females that have recently bred, judging from their brood patches.
Apparently, I am capturing at this site evidence of post-breeding dispersal in females. It is not clear if these birds are looking for a new mate and territory or if they are dispersing to some specific place to molt. It is also not clear if this post-breeding dispersal involves successful or unsuccessful breeding attempts. With respect to today’s bird, however, I have to assume the latter.
Painted Buntings do not arrive here until the first week or so of May. With another week or so of finding a partner, territorial jostling, etc., that means they aren’t even beginning to nest until mid-May, i.e., about 4 weeks ago. It’s possible for a pair to have raised a brood in 4 weeks I suppose, but if so it would be odd for a female to skip town with fledglings fresh out of the nest. Thus, it’s more likely that she was dispersing today following a failed breeding attempt.
Difficult to photograph solo, but that bare skin on the breast is this bird’s brood patch. Incubating birds drop feathers from the breast and belly to place highly vascularized bare skin in contact with the eggs.