Black-headed Gull in California

Black-headed Gull (Larus ridibundus)
Kent Fish Farm, near Mecca, Riverside County, California
29 January 2007
Joseph Morlan

This afternoon, Dan Singer, Robbie Fischer and I decided to try for the Black-headed Gull which had been seen occasionally at the Kent SeaTech Fish Farm at the northwest end of the Salton Sea. We obtained permission to enter the ponds and found several Bonaparte's Gulls (Larus philadelphia) working one of the tanks at the north end of the complex. Most of these birds left when I noticed the immature Black-headed Gull flying in. It landed on the concrete pond and dipped into the water several times. I got it in a Nikon Fieldscope, put my Olympus D-550 digital camera up to the scope and took these photos. The bird was present for approximately 10 minutes from about 2:35 to 2:45pm after which it flew off high to the south and did not return while we were there. Interestingly, there were no Bonaparte's Gulls present during our observation of the Black-headed Gull.

Cathy, Jennifer, and Michelle Tobin had been waiting outside the gate, but came in when I started shouting. While we watched the bird, Jennifer got a good photo of the bird in flight.

Description

A medium sized gull with a plumage similar to an immature Bonaparte's Gull, but decidedly larger. It flew with a languid, lazy style quite distinct from the more energetic Bonaparte's. In flight, the most noticeable feature was the large dark area on the underside of the inner primaries (See photo left). The outermost two primaries appeared white at the tip and grayish at the base. The rest of the underwings were whitish.

The tips of the secondaries were dark and the tip of the white tail was black, giving the bird the appearance of being outlined in black when it was flying. The body, head and neck were white. The bill was orange with a dark tip and there was a faint smudge or spot behind the eye. The bill was longer and heavier in comparison to Bonaparte's Gulls and the dark smudge was fainter. Also the head and forehead was somewhat flatter compared to Bonaparte's. The mantle was pale gray, paler than on Bonaparte's Gull. Dark brown markings were visible on the wing coverts and formed a faint carpal bar on the upperside of the wing (See photos right).

The upperside of the wing showed a white wedge extending from the outer median and greater wing coverts onto primaries P8 and P7. The tips of the outer median coverts were dark, but the dark markings usually seen on the outer median coverts of Bonaparte's Gull were not present.

The legs and feet were orange.

Discussion

This bird was first found by Dave Goodward and Chet McGaugh on 15 January 2007. McGaugh's photo showing direct comparison with Bonaparte's Gulls is here. It has been seen sporadically since, with most observations being either at the mouth of the Whitewater River early in the morning and evening, or at the Fish Farm in the afternoon. I believe this is the first record of this species for Riverside County.

Previously I have seen wintering adults at Stockton and Santa Barbara, but this is my first sighting of an immature Black-headed Gull in California.

As always, additions, corrections and comments are welcome!