Wednesday, March 23, 2016

A Kamchatka Gull in Nova Scotia

The Meteghan Gull
Clarence Stevens Jr. notified Joan Comeau of his find of a Mew Gull (Larus canus) on Febrary 27, 2016 at the wharf in Meteghan, Digby County. The bird was re-found and photographed the next day on February 28 by Joan Comeau on the flats to the east of the wharf at Meteghan (see Google Maps). Joan sent me her photos to get confirmation on the identification and she was thrilled with my reply of "OMG. You found it!!". She had a right to be happy with her photos; there are only small numbers of Mew Gulls that winter in Nova Scotia each year (McLaren 2012). I made the trip up to Meteghan on March 13, 2016 and was able to get a few distant photos (Fig. 1). At the time of writing, the gull was last seen on March 24, 2016 by Mark Dennis and Mike MacDonald.

Figure 1. The Meteghan gull in Meteghan, Digby County on March 13, 2016. Photo by Alix d'Entremont.

The Mew Gull Complex
I wrote a blog post last year about my first North American sighting of a Mew Gull in Dartmouth. I described how the Mew Gull Complex is currently considered to be comprised of four subspecies: L.c. canus (Common Gull), L.c. heinei (Russian Common Gull), L.c. kamtschatschensis (Kamchatka Gull) and L.c. brachyrhynchus ("Short-billed" or Mew Gull). To avoid any confusion, I'll use the Latin names rather than the English names, a practice that seems more typical in Europe. The subspecies that we get in Nova Scotia each winter is canus.

At present time, the American Birding Association Checklist v. 7.8.1 from November 2015 treats all 4 taxa in the Mew Gull Complex as conspecific. Olsen & Larsson (2004) describe kamtschatschensis as distinct and the largest of the four taxa, probably requiring full species status. Some works, such as del Hoyo et al. (1996), Sibley & Monroe (1996), and most recently, Adriaens & Gibbins (2016) suggest that brachyrhynchus should be its own full species, a split that seems more likely to happen than kamtschatschensis being split from the rest.

Brachyrhynchus breeds in western North America and winters along the Pacific coast to California. Canus breeds in Europe and European Russia and winters both in the breeding area and south to the northern coast of the Mediterranean. Heinei breeds from White Russia eastwards to central Mongolia and winters in central Asia, the southern Black Sea and Caspian Sea and further south to the Persian Gulf and some make it to the coast of China. Kamtschatschensis breeds in eastern Siberia and Kamchatka and winters southwards along the coast to Japan, Korea and China. (gull-research.org)

The Gull Research Organization has a section devoted to the Mew Gull Complex complete with descriptions, measurements and many photos.

Subspecific Identification
On March 13, 2016 Ronnie d'Entremont posted photos of the Meteghan gull on the North American Gulls Facebook Page. Lou Bertalan of Germany commented that he thought the gull looked like kamtschatschensis and Maxine Quinton shared that she agreed. Once you carefully study the overall structure and mantle colour, it is evident that this bird doesn't look like canus, our default Mew Gull. Once I was alerted to the possibility of this gull being kamtschatschensis, I sent photos that I had taken on March 13 as well as the great wing photos taken by Mark Dennis on March 14 to Peter Adriaens and Chris Gibbins. Their recent paper entitled Identification of the Larus canus complex takes up 64 pages of volume 38 of Dutch Birding. It is a monumental paper that is essential to the subspecific identification of Mew Gulls.

As chance would have it, both authors were travelling together when they received the photos and suggestion that it could be kamtschatschensis. Chris Gibbins wrote on behalf of both that "the size and jizz, and the upper parts, are obviously good and everything we can see in the primary pattern looks good too." He went on to say that this primary pattern would be very rare in canus.

Elimination of brachyrhynchus is fairly easy based on size and structure which, in comparison to the Meteghan gull, would be small overall, have a rounded dove-like head, and a smaller bill (Fig. 2).

Figure 2. Brachyrhynchus in British Columbia on Sep 21, 2012. Photo by Ronnie d'Entremont.

Mantle Colour
One of the most obvious characteristics of this bird is the dark mantle. In his eBird checklist, Mark Dennis described the colour as "almost as dark as graellsii Lesser Black-backed Gull". When comparing this gull to nearby Ring-billed Gulls, the difference is striking (Figs. 3, 4). Figure 5 shows the relatively pale mantle colour of our regular winter canus, also in comparison to a Ring-billed Gull. While there is a large amount of overlap in mantle colour between Mew Gull subspecies, a dark bird such as this one seems out of range at least for canus, the palest of the four subspecies.

Figure 3. Ring-billed Gull (L) and Meteghan gull (R) in Meteghan, Digby County, on March 14, 2016. Notice the much darker mantle of the Meteghan gull compared to the Ring-billed Gull. Photo by Mark Dennis. 

Figure 4. Left to right Great Black-backed Gull, Meteghan gull and Ring-billed Gull at Meteghan on March 15, 2016. Notice the darker mantle of the Meteghan gull compared to the Ring-billed Gull. Photo by Simon d'Entremont.

Overall Size
Adriaens & Gibbins (2016) generalize that the taxa increase in size from west to east but warn that there is much variation and overlap. Brachyrhynchus is the smallest and then progressively larger are canus, heinei and kamtschatschensis. The authors compare the size of kamtschatschensis as similar to that of Ring-billed Gulls. Figures 3 and 4 show two birds of similar size, strenghtening our argument for kamtschatschensis.

Figure 5. Our regular winter canus (L) compared to a much bulkier looking Ring-billed Gull (R). Note the gentle head shape, large looking eye, visible bill band and in comparison to the Ring-billed Gull, only slightly darker mantle. Photo by Jim Edsall.

Head Shape
In comparison to the other taxa, many kamtschatschensis show an obviously long, sloping forehead and a long and strong bill giving the bird a 'snouty' impression (Adriaens & Gibbins 2016). Characteristics similar to these are more prominent in some photos than others. Figure 6 shows a more gentle looking head shape of the Meteghan gull, but still shows a larger bill and more sloped forehead in comparison to the typical small bill and rounded head of canus.

Figure 6. Meteghan gull (L) on March 12, 2016 and a regular canus (R) in Dartmouth on Feb 27, 2015. Photos by Joan Comeau (L) and Alix d'Entremont (R).

Some photos show the Meteghan gull with an extremely sloping forehead and very large looking bill (Fig. 7). This variability in appearance emphasizes the caveat that we should never rely on a single photograph when shape is an important part of a bird's identification features. Gulls, like many other species, appear to change shape with every posture.

Figure 7. The Meteghan gull on March 1, 2016, showing an extremely sloped forehead and large bill. Photo by Joan Comeau.

Head Pattern
The winter head pattern of the four taxa also differs; although we are in early spring, this feature still deserves a look (see Fig. 7). Heinei typically show a clean white head in early winter, so a late winter bird would likely show a white crown unlike the blotchy streaks on the crown of this gull. (Adriaens & Gibbins 2016)

Bills and Eyes
Most canus & heinei show a complete dark bill-band, but kamtschatschensis and brachyrhynchus both rarely show a complete band, like the Meteghan gull which has a barely visible broken bill-band (Figs. 6 & 7). Howell & Dunn (2007) describe the variation in eye colour of kamtschatschensis as dirty lemon (flecked dusky) to brownish and of the four plates of adults that are presented in their 2007 work, three appear to have irides identical in colour to those of the Meteghan gull (Fig. 8).

Figure 8. The Meteghan gull on Feb 27, 2016. The eyes are actually not entirely black; the iris in direct sunlight is brown, clearly much lighter than the black pupil. Adriaens & Gibbins (2007) found that more than 60% of the kamtschatschensis in their study had irides that were either dark or slightly paler than the pupil. Photo by Joan Comeau.

Primary Pattern
Of all four taxa, canus tends to have the most limited amount of black on P4-5, with only 9% having any black on P4 like this gull. The white mirror on P9 of canus is often larger than that of the same primary of the other taxa. An extremely small percentage (~5%) of canus show an outer web mirror on P9 that is about equal to the length of the black tip as on the Meteghan gull. These small percentages mean that canus will seldom show these wing tip features.

Figure 9. Upper side of both wings of the Meteghan gull on March 14, 2016. Photos by Mark Dennis.

Heinei shows the most black in the primaries. Figure 9 shows that this gull has a black wedge on the outer web of P6 that is slightly less than 1/3 the length of the feather, shorter than is typical in heinei (wedge covers more than 1/3). This gull has a bold white tongue tip to P7, whereas heinei usually has little or no white on the tongue tip on this primary (Fig. 15).

Kamtschatschensis, according to Adriaens & Gibbins (2006), has the most variable primary pattern, but still usually shows a combination of unique features. Most show a complete black band on P5 and some black on P4, like the Meteghan gull and 95% of kamtschatschensis show a big white tongue-tip on P7, as this gull does.

The grey tongues on the underside of the outer three primaries in kamtschatschensis average longer and wider than in heinei. In Figure 10, the Meteghan gull shows a grey tongue on P8 that is about 1/2 the length of the feather and also obvious tongues on both P9 and P10, more than in typical heinei.

Figure 10. Underside of the right wing of the Meteghan gull on March 14, 2016. Photo by Mark Dennis.

Adriaens & Gibbins (2016) warn that the main confusion taxon for kamtschatschensis in terms of primary pattern is brachyrhynchus. Applying the primary pattern identification key provided by Adriaens & Gibbins (2016) results in kamtschatschensis and this was confirmed by Adriaens (pers. comm.). The feature that potentially led away from kamtschatschensis in the late stages of the key was the apparent grey at the base of the outer web of P9 in one photo; the others show an entirely black outer web. In the photo, what looks to be a gray based outer web of P9, might actually be the inner web of P10. This makes it clear that high quality photos of the spread wings are required for accurate results from the primary pattern identification key.

Comparison Photos
Since visual comparisons have already been made with brachyrhynchus and canus, I thought it was fitting to compare the Meteghan Gull with photos of heinei and kamstchastchensis. I would like to thank Aurélien Audevard, an ornithologist with the Ligue pour la Protection des Oiseaux Provence-Alpes-Côte d’Azur, and Kjeld Tommy Pedersen who is a laboratory technician at the Natural History Musem of Denmark for the use of their photos. There are many more photos of all four Larus canus taxa at Gull Research Organization.

Figure 12. Kamchatka Gull (L.c. kamtshatschensis) during non-breeding season in Hokkaido, Japan on February 2, 2010. Note the large bill and sloping forehead similar to that of the Meteghan gull. The eye colour of this bird also seems to be a great match. There is no visible bill band, a feature seen in about 40% of kamtschatschensis studied by Adriaens & Gibbins (2016). Photo by Aurélien Audevard.

Figure 13. Kamchatka Gull (L.c. kamtschatschensis) in Hokkaido, Japan on February 2, 2010. This view shows the tongues on the underside of the outer primaries. P10 has an obvious tongue as does P10 of the Meteghan Gull. Adriaens & Gibbins (2016) describe that about 70% of heinei show no tongue to P10. This particular kamtschatschensis does seem to show longer tongues on P9 and P8 than the Meteghan Gull. Photo by Aurélien Audevard.

Figure 14. Russian Common Gull (L.c. heinei) at Sortedamssøen, Denmark on February 17, 2011. The bill of this heinei shows the typical obvious dark bill band. The barely perceptible bill band on the Meteghan gull is more similar to that of brachyrhynchus or kamtschatschensis. Photo by Kjeld Tommy Pedersen.


Figure 15. Russian Common Gull (L.c. heinei) at Sortedamssøen, Denmark on February 17, 2011. Mew Gulls (L.canus) with limited dark markings on the primary coverts are still aged as adults on the Gull Research Organization webpage. It could point to a young adult, but the primary patterns should still be representative of a full adult. Photo by Kjeld Tommy Pedersen.

Identification Conclusions
Dr. Eric Mills, a long-time birder in Nova Scotia also with world wide experience, saw this bird on March 15, 2016 and notes in his eBird checklist that "In my opinion (after looking at recent literature) only brachyrhynchus and kamschatschensis are possibilities, and this bird is far too large, too large-billed, and has the wrong head shape for brachyrhynchus." Mark Dennis, originally from the UK, confidently says that "[he has] seen many thousands of Common Gulls in Europe and some in Asia but none as dark as this." Perhaps most convincing are the comments from Peter Adriaens and Chris Gibbins, the authors of the most complete and most recent paper on subspecific identification of the Mew Gull Complex, who shared regarding the Meteghan gull that "the size and jizz, and the upper parts, are obviously good and everything we can see in the primary pattern looks good too [for kamtschatschensis]."

The Meteghan gull is clearly not brachyrhynchus, as this taxon would be much smaller overall and would have a rounded head and small bill. The mantle colour appears too dark for the expected range seen in canus. Heinei typically show a clean white crown by early winter, unlike the blurry streaked crown of this gull. The head and bill shape better fits heinei and kamtschatschensis and the bill markings are closer to that of brachyrhynchus and kamtschatschensis. The limited extent of black in the outer primaries of typical canus doesn't fit that of the Meteghan Gull which shows less black than typical heinei. The primary identification key from Adriaens & Gibbins (2016) leads to kamtschatschensis.

My own research, positive comments from local experienced birders along with thoughts from Peter Adriaens and Chris Gibbins appear to confirm the Meteghan gull as kamtschatschensis, a first for Nova Scotia.

Precedence in North America
Other east Asian gulls such as Slaty-backed and Back-tailed gulls have been found in eastern North America with some regularity. An adult Slaty-backed Gull was in Glace Bay, Cape Breton, December 2003 through February 2004 and we've had a minimum of two Black-tailed Gulls since our first was found on Sable Island in May 1997. Records of  two other east Asian gulls in Nova Scotia make our acceptance of a first record of kamtschatschensis that much easier.

Outside of Alaska, reports of kamtschatschensis are very rare, but there are multiple well studied birds in blog sites and eBird that are listed below with links to documentation.

Rhode Island - January-February 2006
Ontario - March 2006
Illinois - February 2008
Ontario - November 2009
Massachussetts - 2010
Massachussetts - 2013
Newfoundland - September 2014 (Birding with Buckley)
Massachussetts - March 2015
Connecticut - April 2015 (eBird checklist 1, eBird checklist 2)

Acknowledgements
I would like to thank Peter Adriaens and Chris Gibbins for their expert comments on the photos that I had sent to them. Maxine Quinton carefully read every word of a draft of this blog and provided me with many excellent suggestions that were incorporated in the final version. Thank you to Joan Comeau, Ronnie d'Entremont, Mark Dennis, Jim Edsall, Simon d'Entremont, Aurélien Audevard and Kjeld Tommy Pedersen for their excellent photos.

References:
Adriaens, P. & C. Gibbins. 2016. Identification of the Larus canus complex. Dutch Birding 38:1-64.

del Hoyo, J., A. Elliott & J. Sargatal, eds. 1996. Handbook of the birds of the world, vol. 3. Lynx Edicions, Barcelona.

Howell, S.N.G. and J. Dunn. 2007. Gulls of the Americas. Houghton Mifflin Company, New York, N.Y.

Howell, S.N.G.,  I. Lewington & W. Russell. 2014. Rare Birds of North America. Princeton University Press

McLaren, I.A. 2012. All the Birds of Nova Scotia: status & critical identification. Gaspereau Press Ltd, Kentville, N.S., Canada

Olsen, Klaus Malling, and Hans Larsson. 2004. Gulls of Europe, Asia and North America. London: Christopher Helm.

Sibley, CG and BL Monroe. 1996. Birds of the World, on diskette, Windows version 2.0. Charles G. Sibley, Santa Rosa, CA, USA

7 comments:

  1. It's great that you do all this research and share - although I'm still pretty confused with the gull world!

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  2. Exciting! Congratulations on pursuing the thesis and giving such a clear and convincing presentation.

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  3. I'd like to agree with Rick Alix. Good summary.

    Cheers
    JanJ (Jan Jörgensen)

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  4. Beautiful photos; wonderful post! Warm greetings from Montreal! :)

    ReplyDelete