27 June 2014

Another Mystery Gull

Well perhaps not a mystery gull, this 1st cycle bird from Sheboygan, Wisconsin may be a very pale graellsii Lesser Black-backed, but Ethan Gyllenhall and I were convinced we'd found a hybrid Herring x Lesser Black-backed as we watched it in the field:

1st Cycle LWHG. Sheboygan, WI. 08 June 2014.
It had just as much, if not more, white in the scapulars than most of the similar-aged Herrings. This, along with the notably pale gray tones were unlike any 1st summer LBBG I've seen. The paling bill, which is not completely unheard of in 1st summer LBBGs, also gave us pause. And what's up with the paling eye? I suppose all of this is possible in a one-year old graellsii, but...

Width and pattern of tailband, and renewed rectrices not typical of LBBG.
Pale sliver notch on subterminal portion of the outer web of P3 not typical of LBBG.
A semi-translucent quality to the underside of the primaries and secondaries is odd for LBBG.

This bird somewhat reminds me of the known-age, known-provenance, 2nd cycle LBBG X HERG found by Blair Nikula back in December 2009 in Cape Cod. 

Green F02 is the offspring of the famous Green F05 LBBG that was paired up with an American Herring Gull on Appledore Island. Here it is shown with one of its chicks, Green F07, from a subsequent brood:


There's no doubt that there's an increasing presence of gulls that appear intermediate between LBBG and HERG in the United States. Some remain skeptical of this hybrid combination, but for the time, I see no better explanation. The primary identification challenge is eliminating Yellow-legged Gull (or vice versa, depending on your perspective). I do feel LBBG x HERG is a much more likely explanation, and seeing that this combination has already been documented right under our nose, we may already be at the stage where we're seeing F2 and F3 hybrids and backcrosses with American Herrings.