2. winter id

The older the easier - that is the truth about Kumlien's Gull identification - or that is not always that simple.

As stated by many people already it is less than ideal that we’re sitting on the Faroes, Scotland, Nederlands, Denmark, Great Britain and other countries in Western Europe trying to determine what is an Iceland Gull and what is a Kumlien’s Gull. This job should be done within their normal range, so that we can say things with a little more certainty.

I’ll write a post on first winter birds later, but the biggest challenge this year are all the highly variable 2. winter birds around (maybe up to 50 % of the total number of birds).  In a previous post I have mentioned the importance of the approach to Kumlien’s Gulls, when it comes to id:

1) If Kumlien’s Gull is a full species then we have to deal with “classic” Kumlien’s Gulls and putative hybrids – kumlien’s x thayer’s and kumlien’s x glaucoides not to mention second generation hybrids!

2) If Kumlien’s Gull is a hybrid swarm between Thayer’s Gull and Iceland Gull then every bird showing the slightest tendencies to some kumlieni-features would be a Kumlien’s Gull (0,000001% Kumlien’s genes).

3) If Kumlien’s Gull is a subspecies that occurred by Thayer’s x Iceland Gull interbreeding but now is more or less isolated from both, you have to define the characteristics for the subspecies in contrast to other subspecies.

I’ll go for the third position. And that leaves us with a challenge to define kumlieni in contrast to glaucoides and thayeri. And this should be done within the species normal range rather than here on the Faroes.
But let’s have a look at in anyways. First we need to know if there is any variation within pure ssp. glaucoide and kumlieni. There is variation within all these subspecies. There are both pale and dark immature Iceland Gulls and Kumlien’s Gull.
Peter Adriaens startes: Many of the immature Iceland Gulls that have brown markings on the primaries, as often seen in Iceland and now also in the Faroes and other places in Europe, actually do not look like the birds typically seen in Newfoundland in winter, and are therefore most likely just ‘brown-winged’ glaucoides.

The easiest way to go about this probably to post some pictures and comment.

Photo taken by Peter Adriaens in Iceland april 2010. He says: "I believe it is 'just' a dark-winged glaucoides, as I did not see any 2nd-cycle Kumlien's Gulls with this type of primary pattern when I visited Newfoundland. The outermost primaries are just too pale, which makes no sense in combination with those extensive brown streaks on central primaries.

So this bird shows that 2. winter Iceland Gulls can be very dark over all and can show a significant tail band. furthermore it has a dark iris. This is quite a contrast to the pale 2. winter Iceland Gulls – see below.

Pale 2. winter Iceland Gull with pale iris.

So let’s say that this represents the variation of 2. winter Iceland Gulls – you can even find even darker and even paler birds. This shows that every bird has to be judged by its overall colouration. Dark birds have to show  even darker and contrasting primaries in order to be safely labeled ssp. kumlieni while pale birds might show less dark primaries – but as long as there is clear contrast within the inner and outer primaries I would call it a Kumlien’s Gull.

A dark bird but note the contrast between the inner and outer primaries and the dark edge made by the primary tips. It is refered to as the J-shape on the outer 4 or 5 primaries formed by the pale inner webs, dark outer webs and dark tip - I would call this one a good Kumlien's Gull - photo taken in Klaksvík.

 

A medium dark Iceland Gull with too few markings on the primaries to be anything other than an Iceland Gull.

 

A rather dark individual with dark primary tips and slightly darker outer webs on the primaries. But note that there is no contrast between inner and outer primaries. The pattern is thus wrong for Kumlien's Gull. So I'd say it's better labeled as a brown Iceland Gull.

 

Same bird as above. On the water it looks like a Kumlien's Gull. But even in this position the primaries are not strikingly dark.

 

A typical Kumlien's Gull. Note the j-pattern and the contrast between inner and outer primaries.

 

Same bird as above. Note how strikingly dark the primaries are.

 

A tricky pale bird. This bird really makes it obvious that all birds have to be assesed by their over all colouration and the contrasts rather than the mere colour on the primaries. Note the obvious contrast in the primaries. So I'd say that this one is in deed a pale Kumlien's Gull.

 

P6 to p10 have slightly darker outer webs and there thus is a ghostly formed J-pattern. So the form of this pattern looks good for a very pale Kumlien's Gull.

 

This bird also shows dark outer webs on the primaries but it is on all the primaries and does not look good for Kumlien's Gull due to the lack of contrast between inner and outer primaries.

 

Again there is a faint ghostly J-pattern on the primaries, so it could be yet another pale Kumlien's Gull.

But then the question is why we do get these birds that do in deed look like pale Kumlien’s Gulls when they are not seen in numbers in New Foundland in winter? Are these in fact pure glaucoides, which are impossible to discern from pale Kumlien’s Gulls? Or is there a true intermediate population somewhere between Baffin Island and Greeland? Or has this anything to do with the undescribed taxon of large gull in northern Russia (Novaya Zemlya and Cape Zhuralev – see note on page 215-216 in Gulls by Olsen and Larsson)…

SiO

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One comment on “2. winter id

  1. Martin G says:

    Hi Silas. Exciting stuff!! You are adding immensely here to an understanding of patterns of variation within glaucoides/kumlieni, and asking all the right questions. Please keep it up, it’s all progress.
    And I find your question about “brown-winged glaucoides” very appropriate. Just where have these been all these years? Apparently not Newfoundland or Faeroe. Or have they been recorded in Europe (wrongly) as kumlieni? Am I right to think the proportions of so-called brown-winged birds are higher this time than in any previous influx?
    Best Martin

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