ARTICLES ON HAWAIIAN AND PACIFIC BIRDS, BIRDWATCHING AND WILDLIFE

An interesting Gull observed on O'ahu.

A first-winter Gull was observed near Laie Point on the windward side of O'ahu by visiting birder Nick Komar from Fort Collins, Colorado on February 15th at about 1:45 pm. Nick stated at the time: "I don't think it was Larus argentatus smithsonianus because it had a notable tail band rather than an all dark tail. Dark secondaries and outer primaries rules out Glaucous or Glaucous-winged Gull. The location was about 2 miles south of Laie. I returned to the spot several times during the following week but did not refind this bird." Subsequent debate and assessment by other birders in the State and on the Mainland (as well as internationally) have resulted in divided opinion with some saying it is an American Herring Gull and others believing it to be a Slaty-backed Gull. Slaty-backed Gull is very rare in Hawai'i, with most records being from the Northwest Chain where the last bird was recorded in January 2001 on Midway.

The following account includes correspondence from various birders on the identity of the Gull, which is still ongoing. All photographs of the bird are by Nick Komar, and where possible or relevant, important features are commented upon. Thanks to all those that have commented on the identity of this bird and especially to Nick Komar for providing the photographs and opening up an interesting identification challenge.

As of January 2004 the gull has still not been definitively identified and it may be that the identity of this individual will never be fully resolved. Any comments on this bird's identification are welcomed and will be included here.

Many of the larger immature Gulls of North America, Asia and Europe are notoriously difficult to identify and some require a feather by feather detailed description to be able to identify them correctly to species. Luckily in this case there are a good set of photographs to help with the identification challenge, however, photographs often do not convey the full jizz or behaviour, or even sometimes the true plumage of an individual bird. Even when there is a fine selection of photographs, as in this case, it is not always possible to identify any particular bird with 100% accuracy. The "O'ahu Gull" is obviously an interesting bird but does pose a hard challenge to identify, and bearing this in mind, the following gives characteristics and plumage pointers to what the bird's true identity may be, although the definitive identification has yet to be resolved, and several of the species dealt with below show some of the characteristics shown by the O'ahu Gull. Descriptive notes below refer to 1st winter birds unless otherwise stated. Those descriptive notes which apply to the O'ahu gull are highlighted in bold in each species account.

Slaty-backed Gull (Larus schistisagus)

A large north Asian gull, which is in fact the only large dark-backed gull in its breeding ranges, although obviously the O'ahu gull is neither an adult nor in its breeding range and so this is no help in the identification. The species is generally stocky with a rounded head, a rather straight and thick bill with a poorly-marked gonydeal angle, and with rather stout but shortish-looking pink to rosy pink legs. Alert birds are said to stretch their necks and adopt a rather pot-bellied stance. The wings are shortish in resting birds. In flight the species appears heavy with a full neck, a rather broad arm with a short pointed hand, and quite slender rear parts. In all ages the outer wing pattern appears streaked with a pale line of dots and the primaries have pale inner webs (except P9-P10) and mid-primaries show broad white tongues, a pattern which is apparently only shown to such a degree by certain hybrid gulls (eg. Glaucous-winged x Western Gull, Glaucous-winged x American Herring Gull). American Herring and Vega Gull are slightly smaller and less-heavy, with slimmer bills and longer wings on the whole.

In general they exhibit a pale throat, chin and hindneck, which often shows as an isolated hooded effect on the head (sometimes half-hood or cap). The mantle and scapulars have scattered new grey and greyish-brown feathers, which usually show blackish triangles, fine black anchor markings, shaft streaks, subterminal bars and pale tips. According to (Olsen and Larsson 2003) the juvenile wing often fades quickly from the first-autumn plumage to strongly worn by February.

First-year Vega Gull is usually browner with a paler head and blackish wing tips, which contrasts with a much paler window. Vega lacks the pale inner webs and the outer wing line of spots. The greater coverts are more strongly patterned with distinct pale and dark bars, which contrast with the dark secondaries. The tertials are blackish with pale notches along their sides which appear concolourous with the wing-tips. The rump is whitish with darker barring against a whiteish tail-base and the broad black tail-bar. In February and March the coverts and rump fade to an almost whitish colour which contrasts storngly with the dark tail and inner primary sub-terminal marks. The species can be distinguished from American Herring and Vega Gulls by a solid brown tail and paler brown flight feathers, with an obvious streaked appearance on the outer wing. The eye becomes paler from about March.

Vega Gull (Larus vagae)

A large gull from northeast Asia, which is often regarded as conspecific with Herring Gull. The size and shape is very similar to Herring and American Herring Gulls, with a front-heavy, round-headed posture, with heavy bill with a distinct gonydeal angle.

First-winters are very similar to American Herring Gull and exhibit a very obvious pale window on P1-P5, a dark-patterned head which often shows a slightly darker eye-mask, and brown patterned underparts. Eastern birds are often paler-headed with a paler face and dark neck-streaks. Compared to American Herring Gull the species tends to be more greyish-tinged, paler and with distinct streaks or spots. The mantle and scapulars are usually paler and show finer and narrower darkish anchor-shaped markings, which appear barred in the field. The tail shows a dark tail-bar which is broad against the white tail-base. The dark tail-bar usually has more white than black mottling in T6, which strongly contrasts with the white tail-base and is a good feature to separate from American Herring, although some show an extensive dark tail as in American Herring. Many Vega Gulls show a densely dark-barred rump: the O'ahu gull lacks this (and some other features) and thus Vega Gull is the least likely of the three species detailed here.

Many show a juvenile-like, rather than fresh-looking, plumage well into winter, and are apparently never strongly abraded before June.

American Herring Gull (Larus smithsonianus)

A large, but generally slim, round-headed gull with a large bill with medium gonydeal angle. The first-winter plumage develops from the autumn and the mix of old and new feathers are often prominant, especially on the scapulars. The head on the whole becomes paler and contrasts with the darker markings on the hindneck and the upper mantle. Sometimes the head appears almost white in winter, which contrasts strongly with the rather uniform brown underbody. In many individuals the bill becomes pinkish with a black tip, recalling Glaucous Gull, although in others the bill remains all-dark throughout the first winter. The tail is all-dark with heavy dark-barring on the rump, although it can show narrow white spots on the tail-sides as well as limited white at the tail-base.

Most of rest of plumage is like juvenile but mantle and scapulars show dark markings which are generally more anchor-shaped, triangular or greyish in colour. With wear the darker median coverts and lesser coverts contrast with the paler geater coverts in pale-patterned individuals.

In conclusion, at present the identity of the O'ahu Gull must remain tentative or unsolved, although from the photographs Vega Gull is unlikely as several features are lacking (see above) and American Herring Gull is likely ruled out by the rump-pattern and the heavily streaked underparts, with no sign of the smooth, velvety complexion of many individuals. Slaty-backed Gull seems the most-likely candidate, however there is a strong likelihood of it being a hybrid individual, and these by their very nature possess a wide range of plumage variation, many of which are undescribed and not fully understood. Hopefully in the future more information on juvenile large Gulls will come to light which may help identify the O'ahu Gull with (some) certainty.

Main Points:

Slaty-backed Gull

1). First-winter at rest: Generally greyish-brown with dilute covert pattern. Mantle and scapulars are grey with dark shaft-streaks or subterminal marks, which appears weaker and unbarred compared to Vega Gull. The head is paler than in juvenile through wear. The bill has a fleshy-coloured base.

2). First-winter in flight: Underwing is contrasting with the coverts muddy-brown in colour which contrasts with pale flight feathers, a dark trailing edge and the exhibition of a "string of pearls" on the wing-tip. The breast and flanks show a contrast with the paler belly and the undertail coverts. As the birds plumage develops the wing becomes bleached, especially on the greater coverts which form a pale midwing-bar. The saddle often appears darker grey with streaks or feather-centres.

Vega Gull

1). First-winter at rest: Mantle and scapulars show a greyish-brown colour with a dark-barred saddle against the juvenile wing. The pale base to the bill starts to develop from late autumn. The upperparts and upperwing show a brown wash and well-marked pattern compared to Slaty-backed Gull.

2). First-winter in flight: Overall brown with conspicuous pale window on inner primaries, as in American Herring Gull. Rump and tail-base white with scattered dark spotting. Tail shows a broad dark bar, sometimes covering much of tail as in American Herring Gull. Underbody brown-mottled or streaked, and thus usually better patterned than most American Herring Gulls.

American Herring Gull

1). First-winter at rest: Darker birds: Retain dark-looking pluamge but usually show paler hindneck. Paler birds: Exhibit greyish-brown head and underparts. the head appears slightly streaked. Underbody solid brown with a velvety complexion. Tail all-dark, with only very faint spots along the edge. Bill becomes paler from late autumn. Many winter birds develop a very pale head against the smooth brown body.

2). First-winter in flight: Paler birds: Pale head contrasts with the smooth brown body. Rump often barred and tail appears all-dark. pale window on inner primaries may be very obvious (especially on West Coast individuals). Darker birds: Head may appear darker or capped but hindneck pale, especially from mid-winter.

"It's not Vega Gull. The structure is wrong, the tail band too broad, the inner p window not as well marked as it usually is. I believe it is a 1y Slaty-backed Gull. The bulky, rather short-winged (at rest) structure, the overall uniformity, the relatively broad tail band with diffuse internal border, the poorly marked inner p windows, the darkness around the head and the largely dark bill are all good for this species in late winter. Has this been recorded in Hawaii before?"

Geoff Carey, Hong Kong, March 17th 2003

"Geoff-Thanks again for your insights into the identity of the Oahu gull. Your experience in Hong Kong and east Asia in general is clearly important. I have not heard back from Peter Donaldson whether there are any records of Slaty-backed Gull (SBGU) from Hawaii. Do SBGU occur regularly in Hong Kong?"

"One reason I leaned away from SBGU was that the depiction in Sibley's new field guide for North American birds (I believe-don't have it in front of me) showed an all dark tail for first-basic SBGU. Looking at the photos in Grant's Gulls, I agree with you that the tail band is most consistent with first-basic SBGU (broad, all dark tail band-see photos 498-500). In Grant, the only Herring Gull to exhibit a similar tail band was L. a. argentatus, but even that had too many white specks in the dark band. I also see your point about the lack of sufficient contrast between the inner and outer primaries. This seems to be a combination of darker inner pp and paler outer pp, compared with Herring Gulls (depicted well in Grant's photo 498). Your comments on the overall shape are very helpful. I wonder if the observation of this gull's feeding behavior (hovering over the water while "walking on the water" and then almost lunging head first for food items under the surface) favors SBGU? I have not seen this with L. a. smithsonianus Herring Gull. Does L. a. vegae do this?"

"What is your opinion about the absolute identifiability of this gull, based on the 6 photos now posted at Christian Melgar's website? Can L. a. smithsonianus be absolutely ruled out (a variability issue)? I hope you don't mind that I have shared your comments with a few others who have expressed an interest in this gull."

Best wishes, Nick Komar, Fort Collins, Colorado, March 24th 2003

"Nick, There are a number of reports of Slaty-backed Gull from the Hawaian Islands. Most are from the Northwest Hawaiian Islands. Some reports are questionable, but we do have both specimens and good photos. I don't know of any photos of immature Slaty-backed Gulls here and I don't know if any of the reports from the main islands are very reliable. I've looked over Grant, Sibley, etc. and it looks like a pretty tough call. Do you have the 'Large Gulls' video? That's the best reference I know of for ID questions like this. It remains a tough call, though. Do you have any shots that give a clear view of the underwing pattern? After looking through my references, it looks like that might be useful."

Peter Donaldson, O'ahu, Hawai'i, March 24th 2003

Peter Donaldson, O'ahu, Hawai'i, March 25th 2003

"Having looked again at the photos, it still seems to be good for SBGU. I note also the legs are rather dark and liver-coloured, which is good for SBGU. As for variability in smithsonianus, I'm afraid that's out of my league. I've passed your URL on to Jon King in California to see if he has any comment. Can you also rule out Western Gull or a Western-hybrid? Not that I have experience of these either! SBGU is regular in very small numbers in HK, but most of my experience of this species has come from winter trips to Korea and Japan (with Jon) specifically to look at gulls. SBGU in 1y plumage doesn't seem to actually have an ALL dark tail; usually there are pale basal corners. However, it is also a very variable species, and a significant number of birds show a tail band, if a very broad and diffusely-bordered one. With regard to the feeding action, I have not noted that to be unique to the species. I do have a number of photos of SBGU, and if you need any to illustrate a paper, I should be able to provide some. I may even have one of a bird similar to this."

Regards , Geoff Carey, Hong Kong, 26th March 2003

"I dragged some more stills off the video (picture 7 - 11 below), and I believe I can show you some better shots of the underside of the wing, and the paleness of the primaries. I am seeing pale inner webs on all the primaries, and pale undersides of the secondaries as well. In fact, there appears to be a "string of pearls" effect on the primaries, reminiscent of what is to come in the adult plumage. Furthermore, these photos show uniformly pale, unpatterned greater coverts, perhaps beginning to fade. As you can see, I am sold on the Slaty-backed Gull identity. What do you think?"

Nick Komar, Fort Collins, Colorado, 26th March 2003

First-winter Gull sp. near Laie Point, O'ahu, February 15th 2003.

Photographs © byNick Komar

Photographs 1 and 2

Note the dark tips to the stretched primaries and pale inner primary panel, as well as the dark tail.

First-winter Gull sp. near Laie Point, O'ahu, February 15th 2003.

Photographs © byNick Komar

Photograph 3

Note the fairly evenly thick bill with only slight gonydeal angle, dark facial mask and ear-covert spot, pale nape and throat/upper breast and streaked breast.

Photograph 4

Note the pattern of the spread wing, the dark tail and virtually white uppertail and rump.

First-winter Gull sp. near Laie Point, O'ahu, February 15th 2003.

Photographs © byNick Komar

Photographs 5 and 6

Again note the dark tips to the primaries, tail pattern and pale panel on the inner primaries.

First-winter Gull sp. near Laie Point, O'ahu, February 15th 2003.

Photographs © byNick Komar

Photograph 7

Note the pale wing panel, dark-tipped primaries and darkish underwing.

Photograph 8

Note the pale breast with obvious streaking.

First-winter Gull sp. near Laie Point, O'ahu, February 15th 2003.

Photographs © byNick Komar

Photographs 9 and 10

Note the underwing pattern, particularly on the primaries, which has a paler band running across the primaries.

First-winter Gull sp. near Laie Point, O'ahu, February 15th 2003.

Photographs © byNick Komar

Photograph 11

Note the upperwing pattern.

The following details of Slaty-backed Gull nesting in North America are from the paper First Breeding Records of Slaty-backed Gull (Larus schistisagus) for North America by B. J. McCAFFERY, C.M. HARWOOD and J..R MORGART, J.R. which was published in 1997 in Pacific Seabirds Volume 24, Number 2, Page 70.
"As a breeding species, the Slaty-backed Gull (Larus schistisagus) is limited to the Asiatic coasts of the North Pacific and the Bering Sea, primarily around the Sea of Okhotsk and along the east coast of the Kamchatka Peninsula (American Ornithologists’ Union 1983, Harrison 1983). The only previous breeding record in North America, in northwestern Mackenzie, has been seriously questioned (American Ornithologists’ Union 1983). In Alaska, the species is a rare spring migrant and summer and fall visitant along the coasts of the Bering and Chukchi seas (Kessel and Gibson 1978). Evidence for breeding in Alaska is limited to a territorial bird at Shaiak Island in northern Bristol Bay on 12 July 1990 (Petersen et al. 1991). We report here the first confirmed breeding records of Slaty-backed Gulls in North America near Cape Romanzof, Alaska. Cape Romanzof projects into the Bering Sea at the western end of the Askinuk Mountains (61 o 49'N, 166 o 5'W) on Yukon Delta National Wildlife Refuge. Beginning 3 km south-southwest of the cape, Aniktun Island runs south for 5.5 km across the mouth of Kokechik Bay. Aniktun is a low, sandy, barrier island averaging about 400 m in width. In 1996 and 1997, the island supported a Glaucous Gull (L. hyperboreus) breeding colony. On July 3, 1996, BJM and JRM visited Aniktun Island. As they approached the island, they saw a Slaty-backed Gull sitting upon a nesting mound near the eastern shoreline, about 2 km south of the island’s north end. The bird’s mantle color was near the dark extreme described by Gustafson and Peterjohn (1994). The gull flushed from the nest when BJM approached to within 500 m. As BJM approached, and after he arrived at the nest, the adult circled overhead and gave alarm calls. The nest mound was 0.25-0.5 m high, and consisted primarily of dead vegetation. The nest was built in an expanse of unvegetated sand, and was located >10 m from the nearest Glaucous Gull nest. The nest bowl contained a single egg, and was very similar in both size and construction to the most well-developed Glaucous Gull nests found elsewhere on the island. BJM photographed both the nest and the adult circling overhead (copies of photographs are on file at the University of Alaska Museum, Fairbanks, Alaska). While censusing the rest of the island, BJM saw both an adult and a third summer Slaty-backed Gull near the south end. Although 138 other gull nests were located on the island (primarily Glaucous Gulls, but also a few Glaucous-winged [L. glaucescens] and Glaucous x Glaucous-winged hy-brids), no additional Slaty-backed Gull nests were found. While BJM censused elsewhere on the island, JRM noticed the incubating bird returning to and settling on its nest. Later, JRM observed a second Slaty-backed Gull, as dark-mantled as the first, landing 5-10 m from the incubating bird. Although we could not confirm their relationship, it is likely that the second Slaty-backed Gull was the incubating bird’s mate. On July 3, 1997, CMH, JRM, and an assistant returned to Aniktun Island to census seabirds. We once again found a pair of nesting Slaty-backed Gulls, with a 3-egg clutch. As in 1996, both members of the pair had extremely dark mantles. The nest was 2 m from a Glaucous Gull nest, within a group of about 10 Glaucous Gull nests which comprised the eastern-most nesting cluster on the island. The Slaty-backed Gull nests found on Aniktun Island in 1996 and 1997 represent the first confirmed breeding records of the species in North America."

References

ALSTROM, P; P.COLSTON and I. LEWINGTON. 1997. A Field Guide to the Rare Birds of Britain and Europe. London.

AMERICAN BIRDING ASSOCIATION. 1997 - 2002 inc. North American Birds. Quarterly reports published within NAB. ABA, Colorado.

AUDUBON SOCIETY. 1988. Audubon Society Field Guide to North American Birds. Alfred A. Knopf Inc., New York.

BEAMAN, M and S. MADGE. 1998. The Handbook of Bird Identification for Europe and the Western Palearctic. Christopher Helm. London.

CRAMP, S. et al. 1977-1995. The Handbook of the birds of Europe, the Middle East and North Africa - Birds of the Western Palearctic. Volumes 1 - 9. Oxford, U.K.

DEL HOYO, J.; ELLIOTT, A.; and SARGATAL, J. 1996. The Handbook of the Birds of the World, Volume 3: Hoatzin to Auks. Lynx Edicions, Barcelona.

ENTICOTT, J. and TIPLING, D. 1997. Photographic Handbook of the seabirds of the World. London.

GRANT, P.J. 1986. Gulls: A Guide to Identification. San Diego. Academic Press.

HARRISON, P. 1983. Seabirds - An Identification Guide. Helm, Kent.

HARRISON, P. 1987. Seabirds of the World - A photographic guide. Helm, London.

LEWINGTON, I; P. ALSTROM and P. COLSTON. 1991. A field Guide to the Rare Birds of Britain and Europe. Harper Collins., London.

LINDSEY, T.R. 1986. The seabirds of Australia. Angus & Robertson, North Ryde, New south Wales.

McCAFFERY, B.J.; HARWOOD, C.M.; and MORGART, J.R. 1997. First Breeding Records of Slaty-backed Gull (Larus schistisagus) for North America. Pacific Seabirds Volume 24, Number 2, Page 70.

MULLARNEY, K; L. SVENSSON, D. ZETTERSTROM and P. J. GRANT. 1999. Collins Bird Guide - The most complete Field Guide to the Birds of Britain and Europe. Harper Collins, London.

NATIONAL GEOGRAPHIC SOCIETY. 1999. Field Guide to the Birds of North America. 3rd Edition. NGS, Washington D.C.

OLSEN, K.M. and LARSSON, H. 2003. Gulls of Europe, Asia and North America. Christopher Helm, U.K.

ROBSON, C. 2000. A Field Guide to the Birds of South East Asia. New Holland . London.

SIBLEY, D. 2000. North American Bird Guide. Pica Press, U.K.

Christian Melgar, Worthing, West Sussex, April 2003.

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