The Kingbird
December 1999, Volume 49, Number 4

Eurasian subspecies of Mew Gull (Larus canus canus)¹ on Long Island

By Andrew Guthrie (1), Angus Wilson (2) and Anthony Lauro (3)
1) 271 King Street, Apt. 3D, Port Chester, NY 10573
2) 4 Washington Square Village, Apt. 2-I, New York, NY 10012
3) 8585 New Suffolk Avenue, Cutchogue, NY 11953

On Sunday, 28 Feb 1999, the authors met on the east side of Shinnecock Inlet, Suffolk County, NY to search for a subadult European Mew ("Common") Gull (Larus canus canus) that Lauro had identified earlier. We were eventually able to carefully study and photograph the gull at close range. To our knowledge this constitutes the first record of Mew Gull in New York away from the Niagara or St. Lawrence rivers. Here we recount the discovery and identification of this bird and review the status of Common Gull in New York State and the northeast.

¹The species Larus canus appears on the A.O.U. and New York State checklists as Mew Gull. The name "Common Gull" refers to the nominate subspecies, L. c. canus, found primarily in Europe. For simplicity, this popular English name will be used throughout the article. Additional discussion of Mew Gull taxonomy is provided below.

Circumstances

As far back as 31 Jan 1999, while scoping Shinnecock Inlet from the west side, Thomas W. Burke had gotten a tantalizing glimpse of an intriguing gull feeding behind the jetty on the east side of the inlet. Only seen briefly in flight, the bird superficially resembled a first-year Ring-billed Gull (L. delawarensis), but Burke was struck by the crisp black tail band, contrasting with the rest of the tail and uppertail coverts, which appeared completely white. Although distance and viewing conditions prevented any closer scrutiny, Burke relayed the observation to several local birders in the hope that they might relocate the gull and obtain better views.

On 6 Feb 1999, Anthony Lauro was birding the east side of Shinnecock Inlet when he noted a mid-sized gull actively foraging in the surf just east of the jetty. Upon seeing the bird’s sharply demarcated black tail band, Lauro recalled the gull seen a week earlier by Burke. In addition, he noted that the bird appeared small, with a dainty head and bill, and flew more buoyantly than is typical of Ring-billed Gull. This combination of features led him to believe it was a first-year Common Gull. Lauro telephoned Wilson and Guthrie, separately, from the field to discuss the identification. We discussed pertinent field marks that we recalled and Guthrie and Wilson read some additional passages from several references including Grant, 1986 and Harris, 1988. Again, however, the gull was seen only in flight and did not allow close scrutiny of the field marks which might confirm its identification.

On Sunday 21 Feb, Lauro and Patricia Lindsay again located the gull flying along the surf line immediately east of the Shinnecock Inlet. They managed to get better looks at the tail pattern, confirming the essentially unmarked uppertail coverts, and were struck again by its small-billed, dove-headed appearance. The bird landed briefly, and Lauro was able to study the pattern of the wing coverts. This second viewing convinced Lauro that it was in fact a Common Gull. Based on additional discussions with Wilson and Guthrie, a remaining concern regarding the gull’s positive identification was that the gray color of the mantle did not appear darker than that of Ring-billed Gull - a field mark highlighted in every available reference. We will return to this issue in the identification section below.

The following Friday, 26 Feb, Gerta and John Fritz and Joan Quinlan were able to study the gull, and they were also struck by its distinctive "jizz" and markings, and agreed that the correct identification was Common Gull.

Based on the gull’s continuing presence, Wilson and Guthrie decided to cut short a potentially exciting Saturday of gulling at the Fresh Kills landfill on Staten Island. The two made the long trek to Shinnecock Inlet, arriving in the late afternoon, walked out to the east jetty, and were soon joined by Lauro. We searched unsuccessfully for the gull for almost an hour. Finally, as the light was rapidly fading, the gull flew along the beach, passing directly over our heads. Based on our experience with three of the four taxa within the Mew Gull complex, we were impressed by its extremely small-headed and thin-billed appearance, the striking tail pattern, and its narrow looking wings. It circled over us once and then flew several hundred yards out to the ocean where it landed next to a typical adult Ring-billed Gull. Our excitement quickly turned to frustration as we realized that the combination of distance and twilight would prevent us from studying and photographing the bird. We had no choice but to return the next morning.

Arriving shortly after dawn the following morning, we again spent one-and-a-half fruitless hours working up and down the beach until, finally, the gull made another brief appearance, this time flying past us to the west and continuing alarmingly far down the beach on the far side of the inlet. After another agonizingly long wait, the gull returned, and this time obligingly foraged close to shore in the cove just east of the jetty. We were able to carefully note and photograph the essential field marks of a first-year Common Gull in flight: the well-defined, clear-cut black tail band on an otherwise white tail, the virtually spotless rump and uppertail coverts and the subdued upperwing pattern. The tail and rump pattern ruled out L. c. brachyrhynchus, the subspecies of Mew Gull found in western North America, which has a strongly barred rump and extensively dark tail in first-winter plumage.
 

	First winter Common Gull, Shinnecock Inlet, Suffolk Co 28 Feb 1999.   Note striking solid black tail band contrasting with the clean white bases of the retrices and the more compact, "hunched" appearance when compared to Ring-billed Gull.   Photograph by Angus Wilson

After a short while, the gull landed and began feeding on the beach, allowing us to study and photograph it at close range. We carefully noted the thin, "weedy" bill, which lacked any obvious gonydeal angle; the gentle, dove-headed and large-eyed appearance; and, perhaps most importantly, we were able to confirm that the lesser and median wing coverts were uniform brown with rounded rather than pointed tips, positively eliminating Ring-billed Gull. We noted that the bird had a number of retained juvenal scapulars, so that the gray mantle was reduced in size compared to a more typical first-winter bird. We believe that this delayed molt contributed to the difficulty in assessing the shade of the mantle compared to Ring-billed Gull, as we will discuss in the identification section.

	First winter Common Gull, Shinnecock Inlet, Suffolk Co 28 Feb 1999.   Note the slender bill, rounded head, distinctive pale mid-wing panel and the retained juvenal scapulars.     Photograph by Angus Wilson

Over the next several weeks, many birders were able to study the Common Gull as it regularly returned to the east side of Shinnecock Inlet where it was first sighted. Later, the gull was relocated further east, near Agawam Pond in Southampton, NY, and was seen both there and at the inlet until it was last reported on 23 March 1999.

Separation of first-year Common and Ring-billed gulls is not simple and care must be taken to use a combination of structural and plumage features. Common Gull averages 10-15% smaller then the corresponding ages and sexes of Ring-billed Gull, and has a smaller bill and shorter and thinner wings (Cramp, 1983). However, the smallest Ring-billed Gulls fall within the size range of Common Gull; small female Ring-billeds particularly, can be problematic, especially when seen together with more typical Ring-billed Gulls (Tove, 1993; Lauro & Spencer, 1980).

The Common Gull at Shinnecock showed the classic structural features. It was smaller and thinner-winged than Ring-billed Gull in flight. When it landed, we could see its more rounded head, and, of particular importance, the short, thin, pointed bill, as opposed to the heavier, more parallel-sided bill of Ring-billed Gull (Tove, 1993; Harris, 1989). The combination of head and bill structure, along with the relatively large eye, contributed to the "gentle" expression exhibited by the Common Gull, in contrast with the "fierce" look typical of Ring-billed Gull (Grant, 1986). The color of the bill also supported the identification. As shown by the Shinnecock gull, Common Gull typically has a brownish-gray base to the diffusely black-tipped bill, as opposed to the generally pinkish based, sharply black-tipped bill of first-year Ring-billed Gull (Grant, 1986; Harris, 1989; Tove, 1993).

In order to firmly establish the identification, we took care to examine specific plumage details. When the bird was in flight, the sharply demarcated black subterminal tail band that is characteristic of Common Gull was obvious. Most Ring-billed Gulls show a more diffuse tail band, with a less clearly defined border and often one or more additional narrow bands along the inner edge (Grant, 1986; Tove, 1993). While this difference is sometimes thought to be diagnostic, it is clear that a few first-year Ring-billed Gulls can also show this tail pattern. The Middle Atlantic Coast regional report of the Winter 1997-1998 issue of Field Notes discussed one such individual, and references another gull studied and photographed by Wilson and Guthrie at Breezy Point, Queens Co., NY in March 1998 (Iliff, 1998). That individual displayed a strikingly sharp tail band, but all other plumage and structural features indicated that the bird was a Ring-billed Gull.

Also contributing to the Shinnecock Common Gull’s distinctive appearance in flight was the relatively muted upperwing pattern. Ring-billed Gulls generally have a highly contrasting upperwing, created by a combination of darker brown outer primaries and secondaries, and paler gray inner coverts, which form a distinctly pale mid-wing panel (Grant, 1986; Harris, 1991).

Perhaps the best single plumage feature for separating the two species is the patterning of the upper wing coverts. Overall, Ring-billed Gull shows a more mottled folded wing, created by the pointed, arrowhead-shaped dark centers and wide white margins of the lesser and median coverts. The greater coverts tend to have more dark markings than on Common Gull and the paler gray base color contrasts more with the darker brown of the wing coverts. On Common Gull, the lesser and median coverts have wide, rounded brown centers and narrow U-shaped margins, and the darker gray greater coverts lack the dark internal markings of Ring-billed Gull, creating a more uniform folded wing. The tertials differ as well; dark brown and more mottled on Ring-billed Gull, with narrow white edges, while on Common Gull the centers of the tertials are a more uniform, paler brown, with distinctly wide whitish edges. (Lauro, 1980; Tove, 1993). It is important to note that this feature is only useful as long as feather wear does not obscure the pattern of the individual feathers, and can be difficult to assess with any certainty unless extended close views can be obtained (Grant, 1986). Close study of the Shinnecock gull, both in the field and from photographs taken at close range, enabled us to confirm that the covert and tertial patterns matched that of Common Gull, and conclusively eliminated Ring-billed Gull.

Another feature often cited for the identification of Common Gull in all post-juvenile plumages, is the perceptibly darker mantle compared to Ring-billed Gull. All references available to the authors highlight this difference as an important mark for field identification; the statements in Peter Grant’s classic Gulls: A Guide to Identification are typical:

"Ring-billed Gull resembles Common Gull….The grey of the mantle is much paler… [In first-year birds], because of the paleness of the grey upperparts, Ring-billed lacks the contrasting dark grey saddle which is obvious on first-year… Common Gulls." (Grant, 1986).

We were initially troubled by the fact that the gray of the mantle on the Shinnecock Common Gull did not appear discernibly darker than that of Ring-billed Gull. There are important points to consider when applying this field mark. Observers familiar with side-by-side comparisons of Common and Ring-billed gulls note that while there is a real difference in mantle shade, often extended views in a variety of lighting situations may be required to correctly assess the relative mantle color (M. Garner, B. Mactavish, pers. comm.) In addition, and perhaps more relevant, in Common Gulls that retain a number of juvenal scapulars, the gray of the mantle feathers can appear paler than normal (M. Garner, pers. comm.)

As stated above, L. c. brachyrhynchus is eliminated by the tail pattern. North American Mew Gulls in first-year plumage have an extensively dark tail and heavily barred rump and uppertail coverts. They also retain substantially brownish underparts well into first-winter plumage, and appear darker mantled than canus. L. c. heinei, included in the "Common Gull" group along with canus, is very similar in all plumages. It tends to have darker gray upperparts, which should be noticeable on a first-winter bird, and is somewhat larger than canus. The distribution of heinei, as discussed below, suggests that its occurrence in North America is unlikely. Another remote possibility for an eastern North American vagrant is "Kamchatka" Gull (L. c. kamschatschensis), the Siberian subspecies of Mew Gull, which in many respects is intermediate between L. c. canus and Ring-billed Gull. "Kamchatka" Gull can be eliminated by details of the tail and rump pattern. Although "Kamchatka" Gull has a dark terminal tail band, it is not as clear-cut as on Common Gull, with the brown color extending up the inner webs of the tail feathers. The rump of "Kamchatka" Gull also shows prominent brown barring, unlike the clean white or lightly marked rump of Common Gull, and the bill is typically pink-based with a sharply demarcated black tip (Carey & Kennerly, 1996).

Mew Gull is found throughout the northern hemisphere, except for eastern North America. There are four subspecies; two of these - L. c. canus, found in western Europe; and L. c. heinei, found in eastern Europe and Russia - comprise the Old World Common Gull. The remaining subspecies are L. c. brachyrhynchus (formerly known as Short-billed Gull), found in western North America; and L. c. kamschatschensis, "Kamchatka" Gull, which is found in eastern Siberia.

L. c. canus is the most numerous of the four subspecies. Its European range and population have been expanding over the last few decades. Iceland was first colonized in 1955, and the breeding population appears to be expanding rapidly. Some 60 breeding pairs in the early 1980’s had risen to 300-400 pairs by the end of the decade (Cramp, 1983; Snow and Perrins, 1998).

Common Gull is a rare but now seemingly regular vagrant to the east coast of North America, although its true status is clouded by a frequent failure to differentiate canus from bracyhrynchus. There are accepted records of canus for Newfoundland, Nova Scotia, Quebec, New Brunswick, Massachusetts, Maryland, Virginia and North Carolina. In several cases the same individual has returned for multiple winters. The majority of North American records have come from the maritime provinces of Canada, suggesting that these birds originate in Iceland or the Faroe Islands, enter North America through eastern Canada, and then either move along the St. Lawrence Seaway - there are 19 records for the Province of Quebec (Bannon and David, 1996) - or filter down the Atlantic seaboard. This hypothesis is supported by a first-winter individual photographed in St. John's, Newfoundland first seen on 20 Oct 1990 that had been banded on 14 Jul 1990 as a chick in a breeding colony in northern Iceland. This same individual returned to St. John’s most autumns until 1995 (B. Mactavish, pers. comm.) The occurrence of multiple individuals is not unprecedented in both Newfoundland and Nova Scotia, and in recent years three to four wintering individuals or more - as many as eight were noted in 1998 - has become typical for Newfoundland. In 1988 a first-winter bird seen in March and again as a second-winter in August is believed to have remained for the summer (B. Mactavish, pers. comm.) Further south, Massachusetts records of Mew Gull fall into two seasonal classes: more than twenty records (including two specimens) from January to the first week of May were attributed to canus, while five records from August to October were attributed to brachyrhynchus. A number of the canus records may represent the return of a single individual (Veit and Petersen, 1993). It is possible, however, that Common Gulls occurring in the mid-Atlantic states originate in the British Isles or mainland Europe, having crossed the Atlantic via a more direct route. Although not involving the same species, this possibility is exemplified by a Lesser Black-backed Gull (L. fuscus) observed on Long Island at Cold Spring Harbor, NY that had been banded in a Dutch breeding colony (de Knijff and van Swelm, 1998). The recovery of additional banded individuals would doubtless shed new light on this interesting question.

There have been five previous records of the Mew Gull complex from New York State. The first two records, 4 October 1986 at the Moses-Saunders Dam near Massena, and 29 November and 4 December 1992, in the Niagara Falls area, were identified as L. c. brachyrhynchus. The third record, 27-29 December 1992, again at the Moses-Saunders Dam, was identified as L. c. canus (Levine, 1998). The New York State Avian Records Committee has recently accepted two additional records of Mew Gull, both along the Niagara River: one 10 Nov 1996 in the gorge below Niagara Falls; and one at the Robert Moses Power Station in Lewiston, Niagara Co. 17 Nov 1996 (Andrle, 1999). These records were accepted by the Committee as Mew Gull, but not to subspecific level.

To our knowledge, the Common Gull at Shinnecock represents the first record of Mew Gull in downstate New York or Long Island, and is the first occurrence for New York State to be documented by a photograph or other physical evidence.

Many thanks to Martin Garner, Julian Hough, Bruce Mactavish, and John Vanderpoel for discussions regarding the identification issues involved, and to Jim Lowe and Paul Lehman for assistance in details of records for New York and New Jersey.

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