Mew Gull

Mew Gull is present in Sonoma County mostly during the winter months, but the earliest arrivals may show up as early as mid-September and birds have been sporadically reported in other months. Fairly common at the coast, usually through mid-April of the following year, but may also show up inland where it favors dumps, lakes, and flooded agricultural fields. The bird above was photographed well inland, at Lake Ralphine in Santa Rosa, which is not a regular hang-out for Mew Gull. Most commonly seen in the county at Bodega Bay, where it mixes casually with other gulls. Also fairly common in the winter at Ellis Creek Water Recycling Facility. Mew Gull attains full adult plumage in its third year. Breeds in Alaska and extreme northwestern Canada. Winters all along the West Coast of the US, and as far south as northern Baja California. Generally considered conspecific with Common Gull (Larus canus canus) and Kamtchatka Gull (Larus canus kamtschatschensis); our Mew Gulls are Larus canus brachyrynchus.

Gulls can be terribly confusing, but Mew Gull is relatively easy to identify (the adults, anyway). The winter-plumage birds we see look like a somewhat smallish Ring-billed Gull (Larus delawarensis), but are distinguished by a number of features. Probably most obvious is the small, dull yellow, unmarked bill--without the dark ring that gives Ring-billed Gull its name (note, however, that Mew Gull in non-breeding plumage may show a hint of a dark ring, as in the bird pictured above). The bill is proportionately smaller than on any gull we regularly see. Also, note the lack of any bulge toward the tip of the bill. Mew Gull has a proportionately small, roundish head, unlike the larger, more elongated head of Ring-billed and other gulls. The eye is dark, whereas Ring-billed Gull has a pale iris (see photos below). The back is usually a somewhat darker grey than in Ring-billed Gull and winter birds tend to show more dark streaking on the head and neck, but head streaking is quite variable from bird to bird. Mew Gull has much more white in the primary tips, and that mark alone can distinguish the birds in flight (see photos below). Both birds have yellow legs (adults). Adults in breeding plumage lose the winter streaking on the head and neck, gain a red orbital ring, and the bill and gape brighten to a clear yellow. But, again, we almost always see winter-plumage Mew Gulls in Sonoma County. In my view, these are most easily distinguished from other gulls by the combination of small size; small, light bill; roundish head; dark eye; and the large white patches at the end of the wings in flight.

Juvenile Mew Gull (roughly July to September of the first year) is a pale, fairly uniformly scalloped greyish brown with an all-dark bill. First winter birds (October of the first year to April of the following year) will show grey on the back but with brownish coverts with weakly contrasting, paler edges; pale grey-brown underneath; pale grey-pink legs. By the first winter, the bill will be pink at the base, dark at the tip. Juvenile Ring-billed Gull will have more sharply contrasting dark wing projections. First winter Ring-billed Gull is much paler (mostly white) underneath. It will, like first-winter Mew Gull, have grey on the back, but the coverts will have much more strongly contrasting scalloping. See the usual guide books for detailed comparisons.

Also see: A comparison of common gull heads in breeding and non-breeding plumages

Selected county sightings: Lake Ralphine (December 3, 2011); Ellis Creek Water Recycling Facility (November 5, 2011); Goat Rock Beach (October 16, 2011, Lisa Hug); Bodega Bay (February 5, 2011). Lake Ralphine (January 10, 2011, Doug Shaw).