Viking Gull or Thayer's Gull in Denmark?

[Kent Olsen]

In this post: viewtopic.php?f=7&t=12&start=20#p3044 another ID than Viking Gull has been suggested based on these photos: http://gulldk.blogspot.com/2012/02/viki ... s-x-l.html

I have now selected some more photos of the same individual: http://gulldk.blogspot.com/2012/03/viki ... -gull.html

It was only seen briefly and at very close range before it flew off. Thus I missed the distant view on plumage and jizz...

Did I throw a Thayer’s Gull away?

Kent

[marsmuusse]

Good question by Peter! Very fresh-looking bird, still in juvenile plumage.
Comments: Ideally I would like to see a complete black bill in such birds (fresh plumage), while here the base of the bill is obviously pale. Also, my first impression was that the bill "looks" slender, emphasized by the very sloping forehead; but, after scrolling down on the page, it shows the head with a Herring in the background, and it indeed this bill is convincingly delicate. Another minor thing: edging of the primary tips is rather limited in this bird.
Peter mentions some good points, and I can only add the solid tail-band, of course the dark solid tertial centres, and frosty greyish appearance, which very well fit thayers.
Food for though...

[adriaens]

Bill colour is not a problem; many birds get a clear pinkish base from late winter on.
The degree of pale edging to primaries is variable too.

Some December birds by Chris:
http://chrisgibbins-gullsbirds.blogspot ... ornia.html

[marsmuusse]

Hi Peter,
Yes, I understand there is some variation within the taxon, I was just hinting to the "ideal situation".
Some more reading:
http://www.irbc.ie/announcements/announce28.php
http://www.irishbirdimages.com/pages/ga ... sgull.html (also from March)
http://birdingfrontiers.com/2012/02/02/ ... yers-gull/ (Febr 2012)
http://thebirdguide.com/gulls/herr_vs_thay.htm (Herring vs Thayers)

[Kent Olsen]

I thought that the overall greyish upperparts contrasting with the brown underparts; unmoulted juvenile upperparts by February; rather smooth brown underparts; sloping forehead with feathering extending on to the upper mandible, pale ring around the eyes was explained by Glaucous Gull influence, whereas the very extensive tail band was explained by the influence of a North Atlantic argenteus Herring Gull

Thus I thought it was a hybrid Viking Gull rather than a Thayer’s because

1) it lacked the cute and slender jizz, but was more like a Herring Gull
2) the forehead was a little to sloped and the bill to long, i.e. it lacked the short bill and round head appearance
3) it had developed some obvious pale on the bill base
4) underparts was a little to mottled; my search image for Thayer’s has more smooth, velvety brown underparts
5) the brown bars on the barred uppertail and undertail coverts were to narrow
6) the primary lacked well defined pale fringes
7) outer tail feathers were to pale and barred
8) the primary coverts were not dark enough
9) the dark mottling on the outer webs of the inner primaries could indicate mixed genetics
10) the dark tips at the inner primaries were not well defined

However, I realise that these features are not a problem for Thayer’s Gull, i.e. my search image has to be adjusted quite some. Would be very interesting to some more comments

[JanJ]

While there are mentioned features as being good for thayeri, the fact that bill colour is not a major problem and that males are less 'cute' - I´m not entierly good with the danish gull being a thayeri, for the reasons made by Kent. That facial look - to obvious, broad and clear pale eyering. The mottled únderparts lack any sign of the smoth uniformly colour. So...

JanJ

[adriaens]

While there are mentioned features as being good for thayeri, the fact that bill colour is not a major problem and that males are less 'cute' - I´m not entierly good with the danish gull being a thayeri, for the reasons made by Kent. That facial look - to obvious, broad and clear pale eyering. The mottled únderparts lack any sign of the smoth uniformly colour. So...

JanJ

One with obvious pale eyering and mottled underparts (California, late January):

ThayersGull_1c_BodegaBay_CA_20110127_067.JPG (350.41KiB)Viewed 11906 times

And another:

ThayersGull_1c_Monterey_CA_20110201_021.JPG (429.74KiB)Viewed 11905 times

[JanJ]

Thanks for the pic Peter! The mottled underparts/flanks - is of course whitin the variation for 1st cycle thayeri. However, I was under the impression that some part of the underparts - usually flank feathers maintain/show a certain degree of uniformly coloured feathers. I´m not aware of having seen such obviously barred axillaries in thayeri. It might be the light in kent´s pic but it looks quite blackish white with primaries concolorous with tertials and tail.
Not rellay questioning the suggested thayeri theory, just pokong around for clues - these are not always so straightforward

JanJ

[lou bertalan]

actually when you mention the face pattern, jan - my immediate impression was of one of those nearctic gull faces with the small dark eyes in the rel. uniform brown head and maybe proportions, hard to explain this impression.

[adriaens]

Underwing:

ThayersGull_1c_Petaluma_CA_20110125_001 (1).JPG (535.64KiB)Viewed 11843 times