Lesser Black-backed Gull
Lake Cunningham, San Jose, California
Sunday 11-02-1997
This morning I decided to take my son, Jeff down to Lake Cunningham in San Jose to look for the immature Lesser Black-backed Gull which had been found there on Friday by Steve Rottenborn. We arrived at mid-morning to find no other birders present. Eventually I located the gull sitting on a black float near the western end of the lake not far from the "Raging Waters" theme park, which was fortunately closed for the season.
We walked around the other side of the lake where we met Mark Miller and we were able to point out the bird to him. I brought some stale bread to feed the gulls and soon attracted a flock of California and Ring-billed Gulls but was not able to bring in the apparent Lesser Black-backed Gull. Eventually the gull flew and joined a flock on the east side of the lake. There we got only rather distant views of the swimming bird. We tried more chumming without any success. Then the bird flew back to the black float. I noticed other birders standing on the pier at the Marina on the south side of the lake viewing the bird, so we drove around and joined them. Here the light was much better and the bird closer. This is where I got my best views. Others seeing the bird at this time included Mike Mammoser, Mike Feighner, Bob Ulvang, and a park ranger.
As Jeff was pestering me to finish and go to lunch, I did not have a chance to study the bird in much detail, but I did take notes upon which the following is based:
The bill was black with a pale tip, which formed an oblique angle at the culmen where it was more extensive than at the tip. In good light, a slightly pale horn color was visible near the base of the upper mandible but under most light conditions this area looked all black. A small amount of pink was visible near the gape and the mouth lining was pink. This was easy to see as the bird was attempting to cool itself by gaping and gular flutter. It was a hot sunny day.
The bill was thick, compared to the California Gulls, but lacked any prominent gonydeal angle as usually found in larger gulls such as Western Gull. The culmen was straight at the base, curving downward rather evenly from a point about mid-way out the culmen. The forehead and crown were very flat, almost blending with culmen at the base. Overall head shape recalled some of the larger gulls.
The crown and nape were streaked with dusky, there was a prominent smudge around each eye, and then a separate more circular smudge near the rear of the ear-coverts. The rest of the head, including the forehead, throat, and ear coverts was white. The eye was neither pale nor dark, being a light tan color in bright sunlight.
The back was dark brown with some dark gray mixed within the individual feathers. The tertial crescent was whitish with obvious dark brown bars extending vertically with respect to the water. The median and lesser wing coverts were brown with clear gray fringes. The greater coverts appeared dark brown, solid for most of their length, but mottled with grayish on the innermost coverts just anterior to the tertial crescent.
At least four black primaries were visible beyond the tertial crescent, each with a very narrow pale tip most obvious on the innermost visible primary and less so on the others.
The underparts were white with dark markings on the sides and flanks. In flight, the underwings were mottled brown and the tail appeared dark with an obvious white rump and uppertail coverts. The bases of the lateral rectrices were white with dark crossbars giving the bird the effect of a broad tail-band in flight. The undertail coverts were white and quite long, extending almost to the tip of the tail. The dark rectrices were tipped with whitish and appeared slightly worn.
The legs were dull pink with some yellowish visible in bright sunlight above the intertarsal joint. Several rectangular tarsal scutes were visible on the front of the leg. Webs were pink.
DISCUSSION
This bird was originally reported as first winter, however Nick Lethaby has concluded that it is actually first summer (2nd calendar year) based on the pale tip to the bill, paler eye, worn scapulars and paler underparts. I would have expected a first summer bird to have a more solid gray saddle than our bird which seems to me to be retaining first year feathers on the back. I speculated that it may be advanced first year (1st spring). The only problem with this idea is that it is now November, which means it either has delayed its molt for six months, or is on a Southern Hemisphere molt sequence.
If accepted this would be the first immature Lesser Black-backed Gull detected in California. The bird seems to fit Lesser Black-backed Gull in all respects, but there is a question about immature gulls of the heuglini/tamairensis group. Adults of these taxa, which are variously regarded as races of Herring Gull, Lesser Black-backed Gull or a separate species, are larger and more robust than Lesser Black-backed Gulls, but identification of immatures is unclear.
The photo of the 1st-winter/1st summer Siberian Gull (L. h. heuglini) on plate 54 of "The Birds of Israel" by H. Shirihai shows a bird with a much paler gray mantle, and dark wedge-shaped dark mantle spots as well as more extensive mottling on the greater wing coverts than our bird.
Plate seven on pg. 66 of "Birds of Kenya" by Zimmerman et al. tentatively attempts to distinguish immature taimyrensis of Lesser Black-backed Gull. The former is shown with a pale base to the bill in 2nd winter while second winter Lesser Black-backed Gull retains an all-dark bill. Also the more extensive mottling on the greater coverts and paler back of taimyrensis (1st & 2nd winter) are shown in the plate. A difference noted in the text is the pale panel near the base of the primaries unlike Lesser Black-backed Gull. In flight I did not note any pale panel there, but also did not specifically look for it. The points are probably taken from Grant who makes them on pg. 94-95 of his "Gulls" book. Grant further comments of the proportionately longer legs of heuglini.
Harris’ et al. deal in detail with Siberian Gull in "The Macmillan Birder’s Guide," stating that the tertials of Siberian Gull are "solidly dark-centered...with very narrow whitish fringes all around (instead of obvious indentations near tips)." These authors also claim that Siberian Gull (Heuglin’s Gull) has darker bases to the outer rectrices. If I read this right, I think our bird is closer to Lesser Black-backed, but I’m not sure of the validity of these proposed characters. I understand that some of the material in Harris’ et al. on this subject has been discredited by researchers in Scandinavia who are working on this same problem.
Another possible straggler to California that should probably be addressed is Kelp Gull. This species, being a Southern Hemisphere species, might explain the apparent out-of-season plumage of our bird. The best photos I could find of first winter and first summer, show a bird with more mottling on the greater coverts and less on the tertials. These are on pg. 157 of the recently published "Seabirds of the World" by Enticott and Tipling.
The only useful photos of 1st/2nd year Slaty-backed Gulls I’ve found are in Grant and I believe that our bird is distinguishable from that species by the pattern of primaries, greater coverts and tail.
However, in all of these similar gulls I wonder what the extent of variation may be. I feel that establishing the identity of the Lake Cunningham gull will be one of the great challenges of California ornithology. I expect that photos will be discussed and analyzed by gull experts around the world before a consensus is reached. In my opinion, this is birding at its finest.
Additional phtographs by Bruce Webb, including pictures in flight have been posted at: http://www.ns.net/~BruWebb/LesserBlack.htm
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Joseph Morlan
380 Talbot Avenue #206
Pacifica, CA 94044