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.
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.
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.
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)…