Saturday, 20 September 2014

That Mew/Common Gull Thing

Lots of comments from the experts coming from different medias, combined with a better understanding of what the photos show, and a better understanding of the Mew Gull complex have shed some light on the unusual gull from Sept 16 (see here for my original post). Just trying to compile all that information in one place to help keep everyone on the same page and to provide a place to look back to if/when it is re-found.

------------------------------------------------------------------------------------

First off, there are 4 sub-species of Mew Gull (Larus canus):

L. c. canus: Breeds in Northwestern Europe (Iceland to Western Russia), winters close to breeding range, and as far away as the Mediterranean. Every winter we get about 3 that fit within this taxa, and some have been banded and traced back to Iceland.

2 Common Gulls (L. c. canus) in St. John's, NFLD last winter. There was a minimum of 4 adults over-wintering in town last winter.

L. c. heinei: Breeds in Northern Siberia to Central Russia, and winters between the Mediterranean/Baltic seas and Eastern China.

L. c. kamtschatschensis: Breeds in Eastern Siberia and Korea, and winters in Eastern Asia between Japan and Southern China.

L. c. brachyrhynchus: Considered a separate species by some authorities. Breeds in Western North America and winters nearby.

Of note, there is common hybridization between canus & heinei where their breeding ranges overlap in Northeastern Europe/Western Russia. And heinei and kamtschatschensis interbreed in central/eastern Siberia.

Newfoundlands first record of Mew/Common Gull was in 1956. The bird was shot in Notre Dame bay (Northeast NFLD), and had a band tracing it back to the White Sea where it was ringed as a chick. As far as I've heard, sub-species ID of the bird was not established based on plumage characteristics, and the specific location in the White Sea is unknown. However, this is within the region of overlap between canus and heinei. And, perhaps coincidentally, Iceland was recolonized by canus sometime in the range of 1955-1958. I've tried tracking down the 1956 specimen, but no luck so far - but may have a lead on getting some photos taken of it in the early 90's. Will post/share if/when that happens!

------------------------------------------------------------------------------------

American Mew Gull (aka Short-billed Gull, L. c. brachyrhynchus) can safely be ruled out by mantle colour, size, bill size/length, and iris colour, etc), so I won't be talking about that subspecies in anymore detail.

------------------------------------------------------------------------------------

Moult of the different Common Gull subspecies:

L. c. canus & heinei: moult to winter/basic plumage is from mid-May to mid-Oct.
Primary moult is what is most easily seen in the field, and the Newfoundland bird was in active primary moult (more on that below). For canus/heinei P1-3 moult from mid-June to mid July, P4-5 by early August, P6-8 around late August, and P9-10 late September/early October.

Secondaries, mid-Aug to late Sept. (when P5-7 shed). Tail completes in early Sept.

L. c. kamtschatschensis: generally later than canus/heinei. Adult moult complete July-Nov.
P1 in July, P9-10 mid-October to mid-November. Peak migration along Eastern China peaks in Oct-Nov (later than heinei).
... but if it was a failed breeder - which is entirely feasible considering the unusual location - it may have begun its moult and migration earlier than average for that subspecies.

------------------------------------------------------------------------------------

Plumage characteristics of the 3 sub-species (most details are based on the Gulls book by Olsen & Larsson):

Generally, they get larger and darker towards the Eastern part of the range.

L. c. kamtschatschensis: A distinct taxon (the largest), probably requiring full species status. Largest male approaches size of small HERGs
Jizz-wise: an over-sized canus/heinei with a more sloping forehead, flatter crown, deeper breast and slightly longer, deeper bill, which often looks long. Eyes generally smaller than in canus/heinei.

L. c. canusL. c. heineiL. c. kamchatka
mantlemedium grey with slight bluish tinge
Kodak 5-6
smoky grey, lacking the bluish tinge
Kodak 6-8 (darker towards E of range)
similar to heinei, or slightly darker
Kodak 6-9, rarely as dark as ad. BTGU
P100-7mm longer than P9;
May have white tip, usually no apical spot
4-10mm longer than P9;
no apical spot
4mm longer than P9;
no apical spot
P10 mirror50-70mm40-60mm; slightly less, no real use40-80mm
P9 mirror20-50mm8-35mm; slightly less, no real use;
creating narrower, more triangular
white spot on wing-tip
20-60mm
P8Very little to no white;
Small % have small mirror
(mainly on inner web)
Very little to no whiteVery little to no white;
black grading to gray at base
P5-7
tongues/moons
10-20mm white 'moons' between
black and grey
Narrower but more distinct white
moons between black wing-tip
and grey primary bases
conspicuous white tongues/moons
P1-4
secondaries
and tertials
grey with whitish tipsP1-5 at most with very narrow white
tips but (owing to darker grey
coloration) appearing more distinct
broader in canus

more frequently has dark markings
near the tip of p4
P4 frequently with dark markings

As in canus, P1-5 have white tips although in many matching the narrower
tips of heinei
Irisdark brown, sometimes with
chestnut tinge or silvery spots
mid-brown to dark-yellow, creating
bi-coloured eye;
often darkish looking at any distance
Billyellowish, with deeper yellow tip and
sometimes a greenish-yellow base;
may show thin dark subterminal
spots or bar
Heavier, more parallel edged;
deeper yellow, often with more
complete dark subterminal bar
dark bill markings often weaker
(and more frequently lacking);
distal part of bill is warmer looking

*if I have time, I may add more details to this table this weekend*

------------------------------------------------------------------------------------
Resources
------------------------------------------------------------------------------------

Check out these links for photos of specimens of each of the sub-species and see that the above plumage characteristics work out:

Check out this blog from Japan for a discussion on their Common Gulls:
"...the largest, heavily built birds are kamtschatschensis is hard to argue with but any expectation that the smallest, lightly-built are birds good contenders for heinei doesn't follow."

Photos on that page show an "obvious kamtschatschensis, the large size and very dark saddle of this individual leave no doubt about this gull".

"A lot is made of wing-tip pattern as a means of identifying the different forms of the group but birds here show such a degree of variation it seems unwise to put much faith in it."

------------------------------------------------------------------------------------
The Newfoundland Bird!
------------------------------------------------------------------------------------




Mantle colour was notably dark. Equal in darkness to the neighbouring YLGU (which has a Kodak of 5-9) - but it is thought that we get the darkest of the YLGU taxa, so the YLGU in this frame and the Common Gull probably had a Kodak in the range of 8 or 9. 

And size in comparison to the HERG was impressive for a Common Gull. It was noticeably smaller/thinner than the HERGs and YLGU, but when I was in the field I ruled out L. c. canus simply based on the size of the bird. It certainly does approach the HERG in size (in terms of heigh and length), but was definitely a more 'attenuated' looking bird.



The iris appears consistently dark. Not sure how much the distance between the camera/bird played a role in this (I was ~36m - gmaps measurement - away from the bird and took these photos at 50x optical zoom, and then cropped them).

Also, the bill is rather long (obviously longer than the American Mew Gull), and is duller on the inner 2/3.

I have a lot of trouble taking in flight shots of gulls with my small super zoom camera, but luck was on my side and I managed to get 4 shots of it flight - all of which turned out to be more or less in focus.

The 4th primary (P4) appears to have a small black mark on the outer web. 

And the black band on P5 is complete

P8 can be seen growing in underneath P7, and appears to have quite a long dark area along the outer web. Again, see that P4 has a black mark, and P5 has a complete black band.

The 'moons/tongues' on P7-P5 are distinctly white and contrast strongly with the black bands.

------------------------------------------------------------------------------------
Other vagrant Common Gulls in NAmerica that were claimed to have been "Kamchatka Gulls"
------------------------------------------------------------------------------------

Massachusetts (2013 and 2010)
https://www.flickr.com/photos/pbtrimble/11802322576/
http://pioneerbirding.blogspot.ca/2010/01/ma-mew-gull-0120.html
http://www.nebirdsplus.com/Mew_Gull.htm

Ontario (Nov, 2009)
http://www.peregrineprints.com/zzzz_Article_2010_KAMG.htm

Illinois (Feb, 2008)
http://www.ilbirds.com/index.php?topic=3154.msg4129

Ontario (March, 2006)
http://ofo.ca/ofo-docs/2006OBRCReport.pdf

Rhode Island (Jan - Feb, 2006)
http://www.ri-avianrecords.org/Home/annual-reports-3/report-1

------------------------------------------------------------------------------------
------------------------------------------------------------------------------------

Important to note, I didn't consider any hybrids from different species/complexes, so am a little narrow minded in this post.

This page from Birds Korea describes some of the variation in Common Gulls and warns us of the potential limits in trying to identify vagrant Common Gulls.

Anyway, right now I'm feeling pretty confident calling this a "Kamchatka Gull". But I will acknowledge that as a birder, I can be too eager to label a name to a bird I see or photograph instead of letting it go as a "sp." or some other unknown. We may never know with 95%+ certainty what this bird is - especially considering the possibility of a heinei/kamchatka hybrid, but hopefully this bird will be re-found with all primaries fully grown and better photos than the current ones. I'll be sure to provide an update if that does happen!


Congrats if you managed to read all this!

References: Gulls of North America, Europe, and Asia (Olsen, and Larsson), and the links that I provided above.



------------------------------------------------------------------------------------
Bonus!

A couple more shots of L. c. canus in Newfoundland last winter:

No comments:

Post a Comment