[cobirds] Horseshoe Lake (Larimer): Red-necked Grebe, unidentified gull

A juvenile Red-necked Grebe was at Horseshoe Lake (northeast Loveland) this afternoon, presumably the same one reported on 1 Nov by Andy Bankert. Common Goldeneye were present (FOS for me), 2 Red-breasted Mergansers and several Bonaparte's Gulls. Complete checklist can be viewed on ebird here: http://ebird.org/ebird/view/checklist?subID=S20495019. Also of interest was a gull I could not identify. My best guess is a hybrid Mew Gull x Black-legged Kittiwake. Unfortunately, no photos were obtained. Anyone looking at gulls this fall should keep their eyes open for this oddity. For those interested, here is a description:

An adult gull superficially similar to nearby Ring-billed Gulls, but slightly smaller, like a Mew Gull. White head and underparts. Mantle (back and wings) was gray, but a shade darker than Ring-billed Gull, like Mew Gull. When floating on the water, the gray mantle was separated from black primary tips by a thick white tertial crescent - much thicker than that of Ring-billed Gull, again like Mew Gull. Head small, white and rounded, like Mew Gull except that it lacked any noticeable streaking or smudging. It also lacked any obvious dusky spot or mark in the auricular area that would be typical of black-headed gulls or kittiwakes. However, it had a light gray patch on the nape, similar to that of Bonaparte's Gull or Laughing Gull, and suggestive of winter plumage Black-legged Kittiwake. The bill was small, but due to great distance, I can't say too much about the bill size relative to the accompanying Ring-billed Gulls or about the color of the bill, except that it seemed to be mostly or all dark, suggestive of young kittiwake or any age Laughing Gull. When it flew off towards Boyd Lake (probably roosting there at night), I noticed a white trailing edge of the wing (i.e. white tips to the secondaries), uniform gray on mantle, fairly limited black on wingtips (more like Mew than either Ring-billed or kittiwake) with two small white mirrors on the outer two primaries (smaller than expected for Mew, more like Ring-billed). One last comment: when it was floating on the water, it was picking food items off the surface (as were the Ring-billed Gulls) and its movements were much more rapid than the Ring-billed Gulls, both with up and down head movements, and with body twists from side to side, giving the impression of a smaller "black-headed" gull like Bonaparte's or Sabine's, or like a kittiwake.

 

So, I could not put a species name on this small white-headed gull. Area birders should keep their eyes open for this at Loveland-area gull hangouts like Larimer County landfill, Boyd Lake, Lake Loveland, Equalizer Lake, Fossil Creek Reservoir, and of course Horseshoe Lake. And all points south.

 

Nick Komar

Fort Collins CO