A very dark Kumlieni or Thayeri...

[totoguti]

Hi All:
My friend Stefán Ragnarsson, currently in Spain has sent me some pics from a very nice gull in SW Iceland. This pics were taken by Ómar Runólfsson.
http://gaviotasyanillas.blogspot.com/20 ... ayeri.html

Here are Ómar comments:

Dear all
Attached are 12 photos of a gull that has been identified as dark L. g.
kumlieni, but is also very similar to L. thayeri. These photos were
taken by Ómar Runólfsson in Keflavík, SW-Iceland on the 29th of January
2012, (see also http://www.flickr.com/photos/omarrun/).

Ómar consider this bird being L.g. kumlieni, and I have translated to
English his reasons for that identification: "This bird fulfill most
of the characteristics as being L. thayeri. What makes it interesting
is the dark eye and the colour of the back is slightly darker than on
L. glaucoides. The patterns of the primaries and the colour is within
the range of L. thayeri, e.g. the black colour of the P5, that is not
supposed to be in kumlieni. However, the jizz of the birds is more
similar to L. glaucoides, i.e. both with respect of size, rounded head
and the bill. Based on these characteristics, it will be hard to
conclude that this bird is a L. thayeri" .

We would be interested to hear your views of this gull
Best regards
Stefán

[Theo Muusse]

The mirror on p9 is supposed to be bordered with black, on the outer web?
That is written on an american site I believe.
Theo

[Dave]

Hi Everyone,

I live in St.John`s,Newfoundland. As many of you know we have a very large population of wintering kumliens gulls. One thing you notice if you look at the variation in our Kumliens gulls is that all supposed Thayer`s Gull characteristics and nominate glaucoides characteristics can occur in a Kumliens Gull, there are no guarantees and nothing is impossible! This is why its very difficult to identify with certainty a Thayer`s Gull or nominate glaucoides Iceland Gull in Newfoundland. When we consider possible THGU`s or glaucoides ICGU`s here we look for prototypes and there are always some birds that have to be left unidentified.

Before getting to the gull in question its important to note the following about adult Kumliens and Thayer's Gulls:

- kumlien`s gull are only marginally paler in mantle shade than Smithsonianus Herring Gull and is maybe about a shade darker than (most?) nominate glaucoides.
- kumliens gulls can have all dark eyes or completely pale eyes, but the majority have noticeable dark flecking in the iris.
- kumliens gulls can have a dark spot or even a broken grey bar on p5! ( although not commonly)
- it's rare for a kumliens gull to have a black subterminal bar on p10
- its rare for a kumliens gull to have an unbroken outer web on p9. When present its usually not dark black and doesn't bleed into the inner web. There are possibly exceptions to this.
- seeing the above two points on the same gull is very unlikely, but I've see at least one example
- Thayer's Gull can have a white tipped p10, does not need a black band or mark on p5 and can show a broken outer web on p9. But p9 will show dark black in the outer web with black bleeding into the inner web.Are there exceptions to this??
- Thayer's Gull mantle shade is marginally darker than Smithsonianus Herring Gull and should appear darker mantled among Kumlien's Gulls and certainly among glaucoides ICGU

Thayer's Gull is extremely rare in Newfoundland and over the last 12 years I've seen just 3 adults that I feel comfortable calling Thayer's. When looking for suspect THGU's among Kumlien's I look for the following

1) a bird with a slightly darker mantle
2) almost jet black ( Herring Gull-like) folded primaries
3) extensive smudgy/cloudy head streaking in basic plumage
4) dark irides or at least an iris with extensive dark flecking. Of course, there are lots of THGU's with pale irides too!
5) black markings on at least p6-p10, with a thick sub terminal band on p6, hopefully extending a little ways up the outer web
6) black sub terminal bar or some dark markings on p10 and something on p5. I'm not sure I've seen a Kumliens with a full black band on p5, so this would be a very good sign,along with other characters.
7) unbroken outer web on p9, with black extending into the inner web in familiar THGU pattern. The ones I really feel good about have inky black coloration on p9, not just greyish black shading. A great majority of even the darkest Kumliens have the mirror on p9 extending through the outer web. Of course, THGU often will have the mirror on p9 extending to the outer web as well.
8) a slightly more robust looking bird with more sloping forehead profile, when compared with Kumliens


Some examples of Kumliens can be found here:
http://birdingnewfoundland.blogspot.com ... johns.html

Thayer's Gulls here ( scroll down for adults):
http://www.pbase.com/jpkln/thayers

My opinion of the bird in question is that it fits well within the variation possible in Kumlien's (albeit at the dark end in primary coloration). Immediately I get the impression of a very dainty, round headed,short-billed bird. Its tough to get a feel for mantle shade, but comparing it to the nominate glaucoides standing alongside it, it would appear to be only marginally darker, thus in line with an average Kumliens. While the primary tips are quite dark,they are more of a dark slaty color and not extensively marked enough for THGU in my opinion. In particular the sub terminal band on p6 looks quite small. Overall the primaries do not look black enough to make me consider THGU. Overall, this bird is very typical of a Kumliens Gull, but happens to be in the darker end of the spectrum in terms of primary color, but not in the same league as Thayer's Gull.

I'm hoping to post photos of three adult Thayer's Gulls that I've seen in Newfoundland and some other more contentious birds on my blog in the very near future. I'll post a link here when I get the article completed.

Sorry for the lengthy response!

Cheers,

Dave Brown
http://birdingnewfoundland.blogspot.com/

[JanJ]

Agree with Dave on the subject bird.

A selection of thayeri pattern

http://www.pbase.com/karlbardon/thayers ... 2&page=all
http://www.pbase.com/karlbardon/thguadults&page=all

Mixture:

http://www.pbase.com/karlbardon/iceland ... 1&page=all

JanJ

[totoguti]

Hi Again:
These words are from Stefán Aki Ragnarsson:

I would like to thank all of those that provided comments on the
identification of the L.g. kumlieni. The very detailed examination of
the photos by Dave Brown were especially useful.
I often see kumlieni gulls in Iceland, but numbers can be variable from
year to year. Sometimes I have seen several kumlieni in the same area
day when going though a big group of L. glaucoides. Individuals of
kumlieni that have so dark primaries are much rarer and I have only seen
one individual of L. thayeri, that I can confidentially label as that
species.

Best regards
Stefán