Here's the most recent example of this season's incursion of Black-headed Gulls:
|Adult-type Black-headed Gull. Baltimore County, Maryland. 14 DEC 2011. by Amar Ayyash|
This BHGU has been in the company of 40+ Ring-billeds at the Hunt Valley Mall in Baltimore County, MD. It was first noticed on 10 December 2011 by Russ Ruffing who momentarily thought he had a Bonaparte's in a Best Buy parking lot. After admiring the red bill, Russ did a double-take and properly identified it as a Black-headed (C. parkin lotus).
Chris West and I observed this larid early Wednesday morning after having driven overnight from the Chicago area. We watched it for about an hour before it picked up and flew a mile east to the Papermill Flats. We refound it on a small pond at Papermill, which coincidentally, held a Black-headed in December of 2010 and then another in February of 2011.
Black-headed Gulls are intermediate in size between Ring-billeds and Bonaparte's. Upperpart coloration matches Ring-billed but with a more silvery look. Although BHGUs closely resemble Bonaparte's, there are some obvious key-features that distinguish the two, especially adults. In addition to the reddish bill, note the blackish underprimaries that adult Bonaparte's never show:
I can't help but wonder what sort of Black-headed numbers we'll see in the United States in the distant future. Although not yet with a prevailing presence in the states, it does seem to be increasing much faster than the still "vague" Little Gull.
I was able to capture a couple of amature videos of this bird. Note its kek-kek call which is considerably different than the smaller Bonaparte's:
Edit: it should be noted that individuals found in the St. John's area do not allow close approach by humans and are rarely found at the local landfill (p.c. Dave Brown).