ML647495106

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iPhone photo. Front bird is Bonaparte's, next bird back is Little.

Observasjonsdetaljer

Continuing second-year bird found by Alex Rinkert on May 21. With large flock of Bonaparte's Gulls. First seen in flock of Bonaparte's Gulls immediately north of railroad bridge at about 2:25 PM, after 30+ minutes of determinedly searching through the Bonaparte's. I don't think we had been overlooking it all that time, so it probably flew in from the beach or ocean, as part of the trickle of Bonaparte's and other gulls continually coming and going between the beach and the river. After we had watched it there for a while, it took off and flew about 150 meters farther upriver, landing among more Bonaparte's Gulls at the bend in the river about 200 meters north of the railroad bridge. As we viewed from the riverwalk at about (36.96738, -122.01449), the Little Gull gave us excellent views, eventually coming quite close to shore along with many of the Bonaparte's. In flight, it was particularly noticeable by the black "M" pattern on its back, bolder than that of the Bonaparte's. On the water, it stood out from the Bonaparte's primarily by its shorter neck and rounder head. The pattern of dark coloration on its folded wings also was a bit more extensive than that of the Bonaparte's. In addition to the dark spot behind its eye, it had a smudgy dark brownish cap on the posterior part of the top of its head. The Bonaparte's had various stages of partial hoods, but all of their head smudging seemed to be blackish, whereas this bird's head smudging seemed brownish-black. It came close enough that its feet were visible underwater, and they appeared dark pinkish-reddish-gray, a bit dingier-looking than those of the Bonaparte's. Also, upon close inspection, its bill was a bit smaller than that of the Bonaparte's, but this trait was not particularly obvious at a distance. Although its shorter neck and rounder head were the most obvious field marks, I (ACB) actually first noticed it at a distance when it directly faced me and opened its mouth, showing its pink interior. That reminded me of Dave Weber's May 23 comment which I happened to read, mentioning that this Little Gull tended to open its mouth and show a pink interior, while the Bonaparte's didn't open their mouths as much and seemed to have a dark mouth interior. I didn't see any Bonaparte's open their mouths today, so I couldn't compare the coloration, but his description of the Little Gull's mouth actually turned out to be very helpful! After I saw it with its mouth open, it turned, and that was when I saw how much shorter-necked it looked. Side by side with Bonaparte's, the size difference was pretty noticeable, too. Overall a thrilling and very cooperative bird, well worth the challenge of searching so hard! It was still there when we left its spot at 3:00.

Additional species

• Bonaparte's Gull Chroicocephalus philadelphia