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adult Glaucous-winged x Herring Gull
Nov 19, 2015. Petaluma, California. Photo by Steve Hampton.

Note the darker eye, mirrors on P9-10, and the large gonydeal angle. Each of these features, alone, are possible on a pure Herring Gull, but their combination suggests Gl-W influence. The clincher is the Gl-W-like head smudging.

Nov 27, 2015. Palo Alto Baylands, California. Photo by Mike Rogers.

Based on the dark in the bill, this is probably a fourth year bird. It seems much like a Herring Gull, perhaps slightly darker-mantled. However, note the pale underside of the far primary. This bird would seem quite white-winged in flight from below. The very pale eye, bill shape and rather light mantle shade point away from Gl-W x Western and toward Gl-W x Herring. The head and neck streaking are also Herring-like, though washed out in the photo.

Dec 6, 2014. Davis, California. Photo by Steve Hampton.

The palish eye, darker primaries, and pale mantle all suggest Gl-W x Herring over pure Gl-W. The other gulls are California Gulls.

Dec 6, 2012. Oakland, California. Photos by Noah Arthur.

This bird suggests something from the Kumlien's camp, especially without an adjacent gull for size reference. However, note the short primary extension (especially for a gull with Kumlien's influence), the very pale eye, the thick dark band at the tip of P10, the pattern in P9 where the dark comes across the inner web, and the pale tone of the dark color in the primaries, which is rarely associated with a Thayer's-like pattern. The head and neck markings also have extensive fine barring like Gl-W and the bill is thicker than most Thayer's. This confusing bird is likely a female Gl-W x Herring.

Dec 17, 2011. Davis, California. Photo by Steve Hampton.

Paler-eyed Thayer's Gull in foreground; adult Glaucous-winged x Herring behind. Adult birds can look superficially like Vega Gulls-- a Herring-like gull with a slightly darker mantle, a dark eye, and a red orbital ring. One key difference, evident here, is the underside of P10 on the far right edge of the photo. Note the silvery tone to the dark color inside the apical spot on the far wingtip.

Dec 27, 2011. Redding, California. Photo courtesy of Ray Bruun.

This one looks like a Herring Gull in mantle and primaries, but a Glaucous-winged in the head and bill. Not the small, dark eye, very thick bill (with dark mark), and head and breast smudging. The rather pale mantle suggests the other parent is Herring, not Western.

Jan 30, 2013. Davis, California. Photo by Steve Hampton.

The pale underside of the far P10 rules out Vega and suggests Thayer's. The heavy bill suggests Glaucous-winged x Herring over Thayer's. Absent a comparison to adjacent gulls (and this bird was alone) and a good look at the wing pattern, it's difficult to rule out Thayer's completely. However, the large bill and gonydeal angle suggests the hybrid.

Feb 6, 2014. Tiburon, California. Photo by Steve Hampton.

Note the dark eye, black primaries, and the underside of the far primary, washed silvery gray. The other gulls are California Gulls.

Feb 7, 2015. Davis, California. Photos by Steve Hampton.

The same bird, revealing a classic mix of Herring and Gl-W features, including a dark eye, black outer primaries, silvery inner primaries, mirrors on P9-10 and a "string of pearls" mimicking Slaty-backed, a pale mantle, and an obvious gonydeal angle.

Feb 21, 2011. Davis, California. Photo by Steve Hampton.

This bird is revealing the undersides of P10 on both wings.

Mar 7, 2009. Cordova, Alaska. Photo courtesy of John Moran.

The dark eye, head smudging, and darker mantle suggest Gl-W Gull, but the darker primaries suggest a hybrid. This photo comes from Alaska, the home of Gl-W x Herring hybrids (sometimes called the "Cook Inlet Gull").