This issue’s mystery species features a study (mostly) in black. In fact, the birds in the photograph are blackbirds (family Icteridae), which would seem to make their identification straightforward. As is often the case with "At a Glance" photos, however, there are features of the birds that seem distinctive and, at the same time, ambiguous. This uncertainty is partly due to the fact that more than one species is represented in the photo.
First, look at the appearance of the bill on the right-hand bird in the foreground. It is stout and distinctively shaped, which is somewhat atypical for a blackbird. Most icterids—Baltimore Oriole, for example—possess relatively long and sharp-pointed beaks, although others, such as the Common Grackle, have relatively stout and gently curved beaks. The blackbird in the foreground, however, has a thick, conical beak reminiscent of a sparrow or certain other seed-eating species. This distinctive bill shape, coupled with the uniformly glossy black appearance of the bird’s wings and body, identify it as a male Brown-headed Cowbird (Molothrus ater). Furthermore, at least two other blackbirds in the photo have prominently cocked tails suggesting that these birds are also cowbirds. The cocked tail of feeding cowbirds is often an easy way to pick them out of a mixed flock of ground-feeding blackbirds.
In addition to the three cowbirds in the picture, there is an indeterminate blackbird in the left rear portion. A careful look at the size and posture of this blackbird suggests that it is slightly larger than the cowbirds in the foreground and may not be that species. Although the bird is partially eclipsed by the bird in front of it, its size and posture suggest that it could be a Red-winged Blackbird, but realistically its identity is best left as uncertain.
The remaining blackbird in the center of the picture is noticeably larger than the other blackbirds. In addition to its significantly larger size, this bird also has a prominent pale, perhaps white, circular area around its vent. There is also a slash of white showing on the folded wing. This bird is unequivocally an adult male Yellow- headed Blackbird (Xanthocephalus xanthocephalus). Even though its yellow head cannot be seen, no other blackbird shares the unique ventral marking around its anal opening, which is actually rich yellow like the head, and white inner wing coverts which, when the wing is extended, take on the configuration of a white wing patch. This feature is present only in males.
This mixed flock of blackbirds is typical of many such flocks seen throughout Massachusetts in fall. Though Brown-headed Cowbirds, Common Grackles, and Red- winged Blackbirds are seasonally common to abundant throughout the state for much of the year, Yellow-headed Blackbirds are rare and tend to be found near the coast in late summer and fall. David Larson photographed this flock on October 25, 2014, in Seabrook, New Hampshire.