Comments on: Hybrid Gulls?

By: Gentoo

Gentoo — Sat, 19 Apr 2008 20:52:21 +0000

Definitely a hybrid. Slate gray wing tips in gulls usually indicate some hybrid origin. The bird appears quite bulky and the tertail crescent is very pronounced. The mantel is rather darkish, about that of a paler California Gull.

My guess is a Glaucous-Winged Gull X Western Gull. A GWGU X HEGU would generally be paler on the mantel. This bird appears to have a rather round head as well. Many GWGU X WEGU hybrids often have shallow, flat, sloping, almost Caspian Gull like head shapes , unlike either of the parent species. This trait is highly variable however. This bill, while appearing small, seems rather stout and blunt tipped.

By: Z Rarestorm

Z Rarestorm — Tue, 18 Dec 2007 20:08:31 +0000

Nice photos.

These are certainly hybrids; GWGU x HERG or possibly GWGU x WEGU. As pointed out, bill size, body structure, and the muddy wash of gray in the primary tips confidently eliminates Thayer’s Gull.

Keep it up.

By: Jim DeWitt

Jim DeWitt — Mon, 17 Dec 2007 07:23:39 +0000

I took a look at Olsen & Larsson. They report that Glaucous-winged do hybridize with American Herring, and have a nice set of photos at p. 163. It looks like in the hybrids, the white spots are on P9 and P10. Your birds show the classic 4-5 white spots at P5-P9. The grey tail, to my eye, is at the limit of Glaucous-winged, but not across it. Winter GWGUs, in particular, can have slightly darker tails.

Bird 1 (photos 1 and 2): The eye color in photos 1 and 2 is typical GWGU, darker tail than bird 2/photo 3, but I’d put it at Kodak Grey Scale 7-8. Faded pink-red eye ring.

Bird 2 (photo 3): Tail is Kodak Grey Scale 6-7, well within range for GWGU. Eye paler, but GWGU eyes can be tawny or olive.

I think we can eliminate Thayers; the bill is too short and heavy.

Interesting birds.