Thayer’s Gull: 2nd winter type in Faroes?

and the ID challenges

There will always by those birds in the Iceland/ Kumlien’s Thayer’s ID challenge that fall between, that defy straightforward identification. This is especially true when vagrant individuals are concerned. This bird in the Faroes is one such. It hopefully helps to educate what the easier ones look like.
  

Rune Sø Neergaard of the Danish rarities committee has been exploring this one. It was seen on one day and these are the only 3 photos of the bird. So what is it? Finder Rodmund á Kelduni writes:

3cy Thayer’s Gull, Sørvágur, the Faroes, 4th of March 2012

“Big and powerful bird compared to most of the Iceland and Kumlien’s Gulls this winter on the Faroes. A few large males of Iceland Gull matched this bird in size but were not as strongly built and did not have as powerful a beak as this bird. Further the bird did also not appear to have be as round-headed as the Iceland Gulls.

The six outermost primaries (p5 – p10) showed distinct and and very clear black markings – also with black on the outer web of p10, which might be a bit a hard to see on the photos.

The tail was entirely black, of the same colour as the primaries. Finally, the mantle seemed darker than on Kumlien’s Gulls.

In the winter of 2011/2012 I saw more than 1500 Iceland Gulls and more than 200 Kumlien’s Gulls of all ages.

Best wishes, Rodmund á Kelduni, the Faroes”

thayer candidate 2012-68-F152012thayersmaagec

Thayerss candidate 2012-68-F152012thayersmaagea

2nd w Thayer's candidate Faeroes 2012-68-F152012thayersmaagebAll photos by Rodmund á Kelduni

Chris Gibbins and MG both gave a response to the bird making the same kind of comments based on these photos.

This is clearly in the zone of inviting closer attention. It looks Thayer’s Gull-ish. Chris articulated it the best around the themes of

  • iris colour
  • build/ structure
  • paleness of coverts and tertials and
  • overall plumage tones hard to assess when photos appear rather dark and contrasty.

We are not saying it definitely isn’t a Thayer’s Gull, but rather it appears to us to be one that falls outside of  a high confidence level for a vagrant 2nd winter Thayer’s and into the uncertain Thayer’s/ Kumlien’s zone. Hopefully it continues to press home the kind of features to look for as there are going to be more 2nd w Thayer’s to be found.

Thanks a lot for these images – it is a very interesting bird.

I think it would be very difficult to reach a confident conclusion about this individual from this small number of images – given its real rarity status, I imagine acceptance requires very sound evidence.

Obviously this is a real problem pair of ‘species’ (Kums v Thayer’s) and the more I look at them the more tricky individuals I seem to encounter. This bird has a number of interesting pro Thayer’s features (especially the depth and extent of brown primary pigmentation, and the secondary bar) but also a number that are much more typically associated with Kumlien’s: the very pale eye would be unusual on Thayer’s at this age, and the structure is much more in keeping with Kumlien’s.   A P10 mirror is more typical of Kumlien’s but this bird has a very small mirror and so is rather like that seen in a small number of Thayer’s.

There is of course much variation and it is possible to encounter birds like this in the range of Thayer’s, but in my opinion we should perhaps be considering only the most water-tight examples as acceptable out of range. With Thayer’s this perhaps means the darkest types that are well away from the overlap zone. The recent Irish  (and Spanish) adult is a nice example of this, as is the Lincolnshire juvenile from last winter –  these are at the darker end of the Thayer’s spectrum and hence rather safe.  Perhaps a similar  approach should be applied to 2w birds.

Interpreting photos is obviously problematic: I’m nervous of assuming that these 3 images in these light conditions (which appear very harsh) reflect the full reality of the birds’ appearance – perhaps the contrasts evident for example between the secondaries and the rest of the wing are a little exaggerated in the one image that we have looking down on the bird.

So, in my opinion (but I stress it is just an opinion) perhaps there is not enough in these three images to reach a firm conclusion for such a rare and difficult bird. You may get different opinions on this bird; such differences help emphasise the core problem –  we are all still learning how to identify Thayer’s at this age

Hope this helps.

Chris Gibbins

 

 

 

One thought on “Thayer’s Gull: 2nd winter type in Faroes?

  1. Rodmund á Kelduni

    This Thayer´s Gull do fit a femal Thayer´s well in build/structure http://gull-research.org/thayers/thayers3cy/3cyfeb002.html

    The variation in coverts and tertials of Thayer´s can match this gull.

    A p10 mirror is not unusual for a Thayer´s Gull at this age, also here there is a lot of variation, they can infackt have a very large obvios mirror on p10.
    http://gull-research.org/thayers/thayers3cy/3cyjan06.html and here http://gull-research.org/thayers/thayers3cy/3cyfeb005.html

    If only the darkest Thayer´s Gulls possible will be accepted i Europe, even though we know that Thayer´s Gulls like this are with in the Thayer´s Gull region, we will not get the actual status of Thayer´s Gulls in Europe. And if we only can accept the darkest Thayer´s Gull possible in Europe, this will raise the question if Thayer´s Gulls can have it´s own taxon or it just can be accepted as L.g.thayeri.

    Regards
    Rodmund á Kelduni

    Reply

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