Thursday, February 19, 2015

California Gull

The top two photographs are of California Gulls. The species breeds in western, interior North America. The eastern-most breeding colonies are in the Dakotas, Colorado, and Manitoba. Most of these gulls winter along the Pacific Coast, from British Columbia south to central Mexico. Only a few winter in the continent’s interior. Wintering coastal populations are interesting because they appear to slowly drift southward during the winter, with juveniles dispersing the longest distances. Off the coast of Washington, adults are normally found close to shore, presumably forcing younger birds out to sea.

As birders become better at identifying gulls, California Gulls are being reported with increasing frequency from the Great Lake, the Mississippi River, and the Gulf Coast (Winkler 1996). Most of these out-of-range birds are expected to be immatures, like the bird in the first photo. The young birds have dark-tipped and relatively thin, pinkish bills. Adults’ bills are also relatively narrow bills with black and red spots on them (see middle photo).
I took the last gull photo a couple of years ago in Duluth, Minnesota. I was perplexed, because this gull’s bill looks “spot-on” for a California Gull. I noticed, however, that the legs were the wrong color—pink instead of gray and the back was too pale for a California Gull (also note the difference in iris color).  Turns out that, not only do young Herring Gulls often have black and red spots on their bills, banding studies show that even older adults often retain black bills spots David Bell (pers. com.). The moral of this blog post is to be careful when identifying out-of-range California Gulls.

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