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Mew/Common Gull - March 13, 2011

Mew/Common Gull at Monaca, Beaver County, PA
 
This adult Mew-type Gull was discovered with a group of 150-200 Ring-billed Gulls by Mark Vass late in the day on 3/13. I was able to get there as darkness fell to confirm its identity and get some pictures... barely. I started at 1/125th of a second at ISO 2500 and it went downhill from there. By the end I was at 1/100th of a second at ISO 10000 and that was good enough only to get a picture that was underexposed by 1 1/3 stops. (I threw all of those away.) So I had to put in a bit of post-processing, which I limited to just enough brightness, contrast, and color correction to make the images reasonable. (No, post-processing is most emphatically not "cheating" - in fact it's absolutley necessary for every digital photo. Please don't email me to argue that point.) I also adjusted all pictures by the same amounts to keep things consistent. I post-process every photo I take... I only mention this here because the exact post-processing can be important information when trying to distinguish subtle features of a bird photographed in poor light. Especially in this case, what's important is to be able to compare the mantle color of the subject bird to nearby Ring-billed Gulls photographed in the same light and put through the same post-processing.
 
Anyway, here are a few photos to get started:

gull_mew_monacapa_20110313_1d4_1_e9h1473w.jpg
Canon 1DMkIV, 500mm f/4L + 1.4x, 1/125 sec. at f/5.6 (manual pushed +1.1 in post), ISO 2500, tripod

gull_mew_monacapa_20110313_1d4_1_e9h1469w.jpg
Canon 1DMkIV, 500mm f/4L + 1.4x, 1/125 sec. at f/5.6 (manual pushed +1.1 in post), ISO 2500, tripod

gull_mew_monacapa_20110313_1d4_1_e9h1495w.jpg
Canon 1DMkIV, 500mm f/4L + 1.4x, 1/125 sec. at f/5.6 (manual pushed +1.1 in post), ISO 2500, tripod

(That's not the setting sun reflecting in the upper right in the photo immediately above... it's a streetlight. It was really dark out.)

gull_mew_monacapa_20110313_1d4_1_e9h1479w.jpg
Canon 1DMkIV, 500mm f/4L + 1.4x, 1/125 sec. at f/5.6 (manual pushed +1.1 in post), ISO 2500, tripod

The following description was submitted to the Pennsylvania Ornithological Records Committee. The record was submitted as Common Gull, Larus canus canus.

(Update: the committee voted with three in favor of Common Gull, and the other four in favor of Common or Mew Gull. The record was accepted as Common/Mew Gull.)

Facts:

Temperature: 35 F
Wind: unknown
Sky: cloudy with occasional drizzle
Time: ~7:20 PM to 7:48 PM
Optics: Leica Televid 82-mm APO with 25-50x eyepiece
Camera: Canon 1D Mark IV Digital SLR, 500mm f/4L IS with 1.4x teleconverter, tripod
Photos or audio recordings: 6 photos submitted, taken from a distance ranging from perhaps 75-100 yards (four of these are above)
Accompanying observers: Mark Vass (finder), Dave Wilton, Shannon Thompson

Observation:

Late in the evening of 13 March, Mark Vass called and said he had a possible Mew Gull on the Ohio River in Beaver County in Monaca. He wanted additional confirmation from someone with experience with the species before claiming the ID. The spot is about 20 minutes from my house, and I estimate I arrived sometime between 7:10 and 7:20 and found Mark still there. Conditions were very cloudy/dark with intermittent drizzle/flurry. Local sunset on 13 March was 7:25pm, so lighting conditions upon my arrival were poor and quickly worsened. Still, it took me no time at all to pick the target bird out of a flock of about 150 Ring-billed Gulls about 75-100 yards from our position, due to its obviously darker mantle. I watched the bird for 2-3 minutes before congratulating Mark on his find, and I started taking pictures. Conditions for pictures were best described as horrible, but I was still able to tease out some slow shutter, high ISO images. I was deliberately underexposing by about one stop in order to maximize the shutter speed, with plans to correct the exposure in post-processing, which I did (along with minor contrast and color corrections). The entire flock was very active. The birds were near a bridge overpass which they were reluctant to float under, and the river, due to recent heavy rains, was flowing swiftly, so the flock was constantly being quickly pushed toward the bridge. As they got within a certain range, they’d pick up and fly a short way downstream and put down again, only to repeat the process in another minute or two. They were very vocal and were bunching up into a very tight flock while on the water, a behavior we’ve witnessed in gull flocks on these rivers in the past which is indicative of an imminent departure to resume migration. Sure enough, at 7:48pm in near total darkness, the flock took off once again but this time did not put back down, instead they turned to the north or northwest, gained altitude, and disappeared into the night.

Description

The following notes are copied verbatim from my web page posted on 13 March a few hours after the sighting:

-- Dark mantle. This bird was so comparatively dark it almost suggested a miniature Lesser Black-backed Gull in among the Ring-bills. When I first pulled up the birds had been flying around and Mark had lost track of it temporarily, but it took me only about 5 seconds to pick it out of the flock once they landed. It was that distinctive. The gull is shown in flight and at rest in comparison to nearby Ring-billed Gulls above.
 
-- Unmarked bill. The first image shows the bird's bill the best - unmarked dull yellow with no trace of a ring. The bill size seemed to be about that of the ring-bills or slightly smaller, but at this light and distance, it was hard to make out its exact shape and size, even with photos.
 
-- Smudged brown on nape and upper chest.
 
-- Dark iris.
 
-- Very limited white on the outer primaries. The first photo shows the primary pattern better than I could see it in the field while tracking it in the scope in the poor light. At first as I watched it in life, I could not make out a mirror on P9 at all. But the photo clearly shows a mirror on P10 and a smaller, much reduced mirror on P9. The terminal end of P8 is pretty much black throughout except for a white spot at the tip. P7 and possibly P6 show very small white tongues which form a limited "pearl" configuration.
 
-- Wide white terminal margins to the secondaries, narrower margins on the inner primaries.
 
-- Extensive tertial crescent on the bird at rest.
 
-- Size: The photo of the bird among the flock of ring-bills shows a bird visibly bulkier than its ring-billed companions, and particularly thick-necked. Though in life, the bird's overall length did not seem to be any greater than the ring-bills. Sometimes it appeared to be smaller, but in some aspects it seemed to be about the same size. Afterwards I thought this perception (sometimes smaller, sometimes not) may have been due to individual variation among the ring-bills it was next to at the time.
 

Discussion:

All of the features described clearly eliminate even an aberrant Ring-billed Gull. The bird is a Mew/Common type. At the time in the field and for a time afterwards, considering the bird’s apparent size and the extensive black in the primaries (particularly P8 lacking any white except at the very tip), I wondered whether this might be a “Kamchatka” Common Gull, Larus canus kamtschatschensis. I posted requests for information to both the PA Birds listserv and ID-Frontiers, referencing my web page, and received only three substantive responses and none in direct response to my posts (rather, they were responses to private messages).

The following features are inconsistent with Larus brachyrhynchus (Mew Gull of western North America) and had initially suggested the possibility of kamtschatschensis: bulky appearance, especially the thickness of the neck, extensive dark in the primaries (particularly P8), bill size apparently equal to nearby Ring-billed Gulls, or at least not noticeably smaller, and comparatively narrower trailing edge to the inner primaries vs. the secondaries. However none of these features were pronounced enough to make the bird a definite kamtscatschensis either. The bird was not big enough, the bill not large enough, the primaries perhaps not dark enough. It seemed that this bird didn’t fit either brachyrhynchus or kamtschatschensis perfectly and instead showed features of both. Well after the fact I realized a better question was actually of L. brachyrhynchus vs. L. c. canus (European Common Gull) and that kamtschatschensis was probably never a real possibility.

All of the problems with calling this bird either brachyrhynchus or kamtschatschensis are better addressed by considering canus instead. The size of the bird and its bill were incorrect for both, but are basically correct for canus. More importantly, the pattern on P8, P9, and P10 actually most closely fits canus, whereas it has to be considered at the end of variation for the other two subspecies. Most tellingly against brachyrhynchus is the apparent gap between the “pearls” on P6 and P7 and the mirrors on P9 and P10. Furthermore the mirror particularly on P9 is extremely limited. Some brachyrhynchus can apparently show this pattern, though, for example see http://www.pbase.com/jpkln/image/131047052. Also the trailing edge of the inner primaries is narrower than typical for brachyrhynchus but perhaps not totally out of the range of variation, for example see: http://www.pbase.com/jpkln/image/119412858. However both features are much closer to the typical canus than to an extreme brachyrhynchus. This taken in conjunction with the bird’s relative size and bulk compared to Ring-billed Gulls seem to indicate that L. c. canus is the correct identification. Though I personally believe canus is a safe identification, I would also agree that this bird as photographed and described may not be separable from brachyrhynchus at the edge of variation and may need to be considered no more specifically than “Mew/Common” type.

Not addressed in the discussion above is separation from the central Eurasian ssp. of Common Gull, L. c. heinei. I do not attempt to make any distinction between kamtschatschensis and heinei primarily because there do not seem to be any currently accepted criteria for definitively separating the two. However if one accepts that the bird is not kamtschatschensis, then heinei may be sufficiently ruled out for the same reasons.

Prior experience:

I have a fair amount of experience with L. brachyrhynchus in western North America (mostly Alaska and Washington) but no experience whatsoever with any Eurasian ssp. of L. canus.


References consulted after the sighting:

Olsen, K.M. and H. Larsson. 2003. Gulls of North America, Europe, and Asia. Princeton University Press.

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

Various websites.

I have also attached a PDF of a portion of the BNA account for Mew Gull detailing its systematics and some of the difficulties that have developed in naming and describing the various populations. However I have not used the common names indicated in this document and have instead opted for the names used normally by American birders: the western American population is “Mew” and European populations together are “Common”. For this reason I have generally indicated the ssp. by its specific name to avoid all confusion.

 



Unless explicitly indicated otherwise in the photo caption, all photos on this website were taken by and are 2003-2013 by Geoff Malosh. Unauthorized usage of these photographs for any purpose is strictly forbidden. If you are interested in using any photo for publication or if you are interested in obtaining a print, contact me at pomarine -AT- earthlink -DOT- net.