Band-tailed Gull (Larus belcheri)
Imperial Beach, San Diego, California
Friday, August 22, 1997
Upon arriving at the Western Field Ornithologists Conference in El Centro on Thursday, August 21st, I learned that the on-again off-again Belcher’s (Band-tailed) Gull had returned to Imperial Beach where it had been present for two days. I made arrangements to drive to Imperial Beach (San Diego) with Gary Rosenberg and Mike San Miguel early the next morning. We left about 5am and arrived at the north side of the Tijuana River mouth about 7am. After searching the gull flocks across the mouth without success, Mike located the Belcher’s Gull standing on a rise adjacent to a channel to the northeast of the mouth. A portion of this rise is apparently a restricted area during the nesting season for Snowy Plover and Least Tern, however I was told that the earlier access restrictions had been removed because the nesting season was over and that the warning signs had been removed.
We lost track of the bird as it disappeared behind a rise, but Mike located it again on the wet sand flat to the east. We then watched the bird foraging actively and swimming in the channel for the next two hours. During this time we were joined by Brad Schram, Don Roberson and Rita Caratello. Many photos were taken by Gary Rosenberg, Brad Schram and Don Roberson.
After about two hours the bird finished foraging, flew to the south side of the river mouth and rested with a flock of Western Gulls.
The following description is based on memory and on discussion with the other observers at the time.
The head was sooty-black with some smudging on the lower border of the hood and some dingy gray smudging throughout the head area. The feathering on the chin and at the base of the bill was grayish-white, most prominently in the lores, but the dark on the crown extended down all the way to the culmen dividing the white area on either side. Very striking were the broad white eye-arcs above and below each eye. These arcs almost connected behind the eye, but opened up in front of the eye, somewhat reminiscent of Franklin’s Gull.
The dark hood contrasted strongly (despite the smudging noted above) with the pale gray neck, breast and sides. The breast and sides were irregularly smudged with darker gray all the way down to the belly, which became gradually paler until it blended with white on the lower belly and undertail coverts. These undertail coverts were rather long, concealing much of the underside of the tail.
The mantle was sooty-black, the same color as the head, but in strong sunlight showed faint brownish tinges to the wing coverts. In general the back appeared to be clearly darker than that of the "wymani" race of Western Gull, but not jet black. The mantle darkness varied depending on the orientation of the bird with respect to the sun. On the folded wing, the tips of the secondaries appeared tipped with white, and the tips of the inner primaries were also white (visible in flight). However, the outer three primaries had no white tipping and looked slightly brownish and somewhat worn compared to the next two or three primaries which had very narrow white crescents at the tip, visible only at extremely close range through a scope.
The tail was white at the base, including the uppertail coverts, but the distal half of the tail formed a broad black band. All rectrices had broad white tips (broader below than above). According to Guy McCaskie, the tail was in molt, but I did not notice this. Perhaps molt has been completed now. Photographs should clarify this.
The bill was very striking. It was long, and moderately heavy. Yellow at the base with a black ring at the gonys and a striking red tip anterior to the black. The nostril was fairly long, and the septum was perforate (I could see through the bill). The culmen was fairly straight along the basal 3/4ths, arching down at the tip. The gonydeal angle was moderately conspicuous, but there was no obvious bulging to the lower mandible.
The legs were quite long, with prominent intertarsal (ankle) joints and the webbed feet were also clearly yellow.
In flight the underwings appeared whitish on the coverts and dark grayish on the undersides of the flight-feathers, becoming blacker on the outermost primaries. Most secondaries had broad white tips but some inner secondaries lacked this and were probably from a previous generation of feathers. There were no white mirrors in the primaries.
BEHAVIOR: The bird spent much time flying directly up hovering and then dropping soft-shelled clams on the mud and extracting the meat from them. It was quite skilled at this method of feeding. Brad said these were "Butter Clams" and that they had thin shells which break easily. The Belcher’s Gull also appeared to dominate nearby Ring-billed Gulls, occasionally stealing their food.
It had an odd habit of running long distance along the beach with a tripping gait that seemed almost plover-like to me. I recall someone had mentioned that it was limping, but we saw no evidence of that and the bird appeared healthy to me.
After feeding the bird often swam in the channel, but did not appear to be bathing. It did find clams underwater occasionally. Sometimes the very tip of the bill appeared paler red caused by a drop of water which I believe was secreted from the nostrils.
Although we were able to get quite close to the bird, it seemed neither more nor less wary than other gulls in the area.
DISCUSSION:
The AOU regards Olrog’s Gull (Larus atlanticus) of the Atlantic Coast of South America as a separate species. It is quite local and rare and does not have the dark hood of Belcher’s Gull during the non-breeding season. The AOU retains the name Band-tailed Gull (L. belcheri) for the Pacific Coast population although I prefer the name Belcher’s Gull for clarity since Band-tailed Gull has been applied to Olrog’s Gull. I feel the dark hood of our bird effectively eliminates Olrog’s Gull.
There is one prior record of Band-tailed Gull in California, a bird well seen and sketched by a single observer present on San Nicolas Island, 9 Nov 1987-28 Jan 1988. This record was narrowly rejected by the California Bird Records Committee (Western Birds 26:1-33, 1995) by an 8-2 vote. The two dissenting votes felt the identification was not fully established.
Prior records from Florida (e.g. see photos in American Birds 29:681, 1975) and Panama are included in the AOU Check-List (7th edition) with the caveat that "The possibility of the Florida birds being escaped captives or man-assisted vagrants remains." The ABA Checklist committee placed the species on their supplemental list of species which might be wild or escaped. Following an ABA rules committee decision that birds on the supplemental list were countable for ABA listing, the ABA checklist committee apparently abolished the supplemental list and all birds on it currently stand as rejected and not countable. At least that is my understanding.
I don’t think there is any way of knowing for sure how this bird got to California, but the prior record from San Nicolas suggests a possible pattern of occurrence. Ship assistance is always a possibility although Murphy (Oceanic Birds of South America, pg 1057, 1936) comments, "While the Simeon (Band-tailed) is often seen in company with the Kelp Gull, I have never observed it following in the wake of vessels as the larger species does everywhere along the Peruvian coast."
According to "Handbook of Birds of the World" (Vol 3, pg 601, 1996) the species migrates from breeding grounds between N Peru and N Chile, north to N Ecuador and S to Central Chile (around Valparaiso). The Handbook also states that this species is "Vulnerable to the effects of El Nino." However documented cases of long-distance vagrancy attributable to El Nino are scarce.
The molt, plumage and age of this bird has been discussed by McCaskie and by Corben. McCaskie concludes that it is a second year bird exhibiting a molt sequence off-schedule for a Southern hemisphere species.
I belive the bird was originally found by Douglas Shaw, and Bob Brandriff and identified as a Band-tailed Gull by Kimball Garrett based on the descriptions of the original observers. Another more distant photo of the bird is at <http://www.rdrop.com/users/green/quiz21.jpg.>. Additional excellent photos may be viewed at the California Bird Records Committee photo gallery here.
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Joseph Morlan
380 Talbot Avenue #206
Pacifica, CA 94044
