White Gull I.D.

[Colin Key]

There has been an "odd" white gull reported from the salinas at Tavira in the eastern Algarve for the past three weeks or so. I have been sent numerous distant, digiscoped (and mainly 'orrible) shots from various people for my opinion. The photos looked so different that I found it difficult to believe that they were of the same bird.

The attached photo is the first decent shot I have seen; it was taken by Peter Dedicoat on 14th May and has been identified as a leucistic individual. I won't say which species, but would like opinions as to what you think it is (are you there Jan?).

Thanks in anticipation,

Colin


http://i118.photobucket.com/albums/o100/Passarinhos/image002-1.jpg

[JanJ]

Hello Colin.
That is a tricky one - but I would rule out Glaucous Gull instantly, the big eye, long Yellow-legged Gull legs but not mentioning the bill size/shape since it doesn´t entierly rule out a Glaucous alone - but not that good either.
Herring seems wrong - in fact Yellow-legged - Caspian doesn´t seem right either. One possible candidate could be Greater black-backed Gull, but the eye seems on the big end and jizz - long tibia bill shape seems wrong for that species to.
Primary projection looks short (we don´t see the tail) but queation is , can it be trusted due to the wear of this snowy-white odd looking Gull.
I´m stuck, not being able to deliver.

JanJ :beer:

[Red-eyed Video]

Lesser Black-backed?

[AndyB]

Interesting bird. At first glance I was going to buy Glaucous but as Jan points out there are some structural oddities.

Not the same as your bird but here's an interesting hybrid from CA:
http://www.pbase.com/tgrey/image/27606279

[Colin Key]

Thanks Jan, Dave and Andy for your input. This bird has tentatively been identified as a leucistic Yellow-legged Gull (L. michahellis); that does not look quite right to me from the shape of the bill, especially the lower mandible. That could however be due to the fact that this bird has some genetic defects which might extend to physical features in addition to just plumage and bare part colouration. I have contacted the photographer and asked what his criteria for I.D. are but have not yet had a response.

The original poor quality digiscoped photos I saw were mainly at a much greater distance and although the bird was in the company of Yellow-legged and Lesser Black-backed Gulls it was not easy to get a clear indication of its size. The original thinking was that it was either an Iceland Gull (2nd cal. yr.) or a leucistic form of a commoner species. I did see a high magnification (very blurred) shot of the head and front part of the bird in a more "hunched" pose and with a slight pinkish-brown tinge which made me think of 2nd year Glaucous (of which we have had a few individuals in the Algarve this spring).

I have not had a chance to see the bird myself but will try to do so this coming weekend if it is still around.

Any further suggestions or comments will be much appreciated.

Colin :err:

[gawnbirding]

This is an albino or leucistic individual. It is evidently a large "herring-type" gull, based on the location my quess would be Yellow-legged which I assume is the commonest local large gull. The long legs and bill shape tend to support this; it has the right "gis". In Ontario where I do most of my birding the most frequent albino is Ring-billed Gull, no surprise as it is also the commonest gull.

Regards

[JanJ]

From a copy of the bird I added the colour of an, in this case, adult Yellow-legged Gull and came out with a fairly good example of, although a slightly atypical, but not so bad YLG.
I can of course see the tentative YLG with those legs and being the more natural choise due to location it might well turn out to be a such a one.
The headshape and bill shape and lenght of it might seem a little bit odd for YLG but...

JanJ

[Colin Key]

Thanks again Jan (and "gawnbirding") - it is looking more likely as a Yellow-legged/Herring "type", but the bill still worries me - it is not really heavy enough and the lower mandible looks truncated or deformed.

Here are some interesting links provided by "Arade" (Nelson F) on the Portuguese "Fórum Aves":


http://www.pbase.com/crail_birder/image/77616378
http://www.birdforum.net/attachment.php?attachmentid=126022&d=1202998706
http://www.gos.org/sightings/28-gulls/herg.html

Colin

[Colin Key]

I have just received two more photos of this bird from Ray Tipper (an Algarve-based birder, photographer and tour leader). They show the bird quite close to what I believe are sub-adult Yellow-legged and juvenile Lesser Black-backed gulls. The bill looks rather thicker in these shots, but the bird itself looks relatively small and extremely long-legged. To my eye (although I have still not seen the bird in "the flesh") it also looks a bit "unwell".

Any further thoughts?


Colin


http://i118.photobucket.com/albums/o100/Passarinhos/WhiteGull1.jpg


http://i118.photobucket.com/albums/o100/Passarinhos/WhiteGull2.jpg

[beltonbirder]

Could this be a leucistic Herring Gull?

[Colin Key]

Could this be a leucistic Herring Gull?


You would be hard pressed to distinguish between a leucistic Herring and Yellow-legged Gull. Herring Gull is a rare bird down here. There is still the problem that it is smaller than a Herring/Yellow-legged "type".

Colin

[JanJ]

Hi Colin.

Gulls like this one - which probably is not well - are ver difficult, and I would say that the really one character that would suggest either way (HG, LBBG and YLG) are the long legs, thin long tibia) which looks better for YLG or Caspian , don´t see Caspian in this one though.

JanJ

[Colin Key]

Hello Jan,

And thank you once again for your expert in-put. Funny you should refer to Caspian because that originally came to my mind because of the relatively slim, almost parallel-sided bill without a prominent gonys.

I would probably agree now that, irrespective of its small size, a Yellow-legged is statistically the most likely lineage for this bird. However, this individual is clearly 'abnormal' in the literal sense (in its leucism and probably other physical attributes) and I think that we might have to "put it to bed" without arriving at a definitive I.D.

Regards,

Colin :confused:

[Josh Jones]

Sorry just chipped into this thread late; my initial impression of the original photo was Yellow-legged Gull. Of course on range this is also massively likely!

I don't agree that the bill should suggest Caspian; it is too short and stubby for one.

[Colin Key]

Have just received this photo of the problematical "white gull" in a rather different pose. This new shot appears (at least to me) to show a rather "fuller bodied" bird and the bill looks much heavier and with more prominent gonys (but that could just be the oblique view). Some observers have suggested that slightly coloured areas of the plumage could be due to dirt. Without the other birds present for size comparison I am again back in the Glaucous camp, but am equally prepared to write this one off as an "oddity", although statistically Yellow-legged would make more sense (but statistics aren't perfect!!).

Photo by Peter Dedicoat:

http://i118.photobucket.com/albums/o100/Passarinhos/IMG_1423-White-gullLowres.jpg

Colin

P.S. This might be the last photo, I'm sure you're all pleased to hear :biggrin: