Yellow-Legged or Caspian Gull, UK (1 Viewer)

Mole1 · Jul 26, 2010

Please see attached a number of photos of the 1st Winter Gull in Devon that has been identified as Caspian, although it doesn't seem to be clear cut! On site today, someone mentioned to me there were doubts about the id, and having checked my photos when I got home, it seems that this is a YLG.

I commented in the field that the bird didn't appear long legged enough for a CG and did look like YLG at certain angles, but then there were other times when it looked like it had to be CG! Anyway, the underwing doesn't appear to be white enough for CG and there are a few other anomolies which don't fit CG. Is YLG the safest id for this?

Thanks in advance

Mole1 · Jul 26, 2010

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Mole1 · Jul 26, 2010

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Brian J Small · Jul 26, 2010

Hi Mole

For what it is worth, IMHO this is a Yellow-legged.

Structurally, I feel this is a better fit - note for example the bill which just looks right for YLG. I feel there are plumage features which you have no doubt sussed which are better also (for example the pattern of the g. covs).

Brian S

Cristian Mihai · Jul 26, 2010

I would say Yellow-legged too.

Matt Prince · Jul 27, 2010

Ok for those with lesser experience of the species - myself

- perhaps we could actually have a breakdown of these features.

beak - It looked long (perhaps an suggestion of the head shape) maybe not as slender billed as some extreme Caspian but still slender.
legs - [ it was sat when i was there

] not as long legged as expected
head - looked the right shape for caspian, "snouty"
clearly defined neck band
underwing - not as pale as expected
tertials - with the strong white tip marking aren't these typical of caspian gull and atypical of yellow legged gull
Are you saying that the pattern of the greater coverts is a better fit for YL? I thought YL had stronger chequering (I was flicking to and from the text book and I can't say I was convinced either way on this one).
Mantle - this didn't contribute the typical three colour 'grey brown black' shown in the Helm guide.

I can appreciate that there are features here that are swaying experienced observers away from CG, but I'm surprised that you're so quick to ID is at YLG when many of the features (in particular the tertials and head shape) don't seem a good fit.

Regards,
Matt

Brian J Small · Jul 27, 2010

beak - It looked long (perhaps an suggestion of the head shape) maybe not as slender billed as some extreme Caspian but still slender - there is no reason why YLG can't have a slender bill, but on this bird it still seems to droop at the tip

legs - [ it was sat when i was there

] not as long legged as expected - leg length is not necessarily a feature to separate cach from mich

head - looked the right shape for caspian, "snouty" - there is no reason why YLG can't have a slender head, it is just that it still a little 'lumpy', plus it has the 'masked' effect typical of juv michs around at the moment

clearly defined neck band - is this good or bad for cach?

underwing - not as pale as expected - but probably better for mich

tertials - with the strong white tip marking aren't these typical of caspian gull and atypical of yellow legged gull - variable in both (and some overlap in pattern with some LBbG

Are you saying that the pattern of the greater coverts is a better fit for YL? I thought YL had stronger chequering (I was flicking to and from the text book and I can't say I was convinced either way on this one). - I would say that the greater covert pattern of this bird is good for mich; it has the blobby notching on the inners which are not present on the outers

Mantle - this didn't contribute the typical three colour 'grey brown black' shown in the Helm guide. - the colour and tone on your bird is pretty much what I would expect for a juv mich; some of the scapulars on your bird seem worn and faded already

Brian S

Gavin Haig · Jul 27, 2010

Matt Prince said:
Mantle - this didn't contribute the typical three colour 'grey brown black' shown in the Helm guide.

Hi Matt. This feature would not become evident on a Caspian Gull until later in the year. For example, the 'grey' is contributed by second generation mantle/scaps. Juv Casp and YLG mantle/scaps are very dark (as shown by the Blackhill bird). In Caspian Gull these would be moulted out later in the summer/early autumn, giving rise to part of the three-colour appearance you mention. In other words, you wouldn't expect to see it right now.

The Kerreran · Jul 27, 2010

::Enter, Stage Left, with large oar over shoulder::

Having spent an hour looking at the bird on Saturday, I have to admit I find myself rather surprised by these photos! The gull I saw had a VERY white underwing, for example, with only a little light marking; nothing like what is shown here. It's legs were markedly longer than anything else present, with a belly bulge behind them, and the head shape was pretty classic Caspian. The eye mask below and behind the eye, with a smudge on the ear coverts, is also fine for Caspian [their broader, more diffuse mask wears quickly, lasting longest around the eye]. Light grey-brown streaking on the crown but not the forehead also served to contrast the very black bill when the bird was head-on.

The bill was thicker than I expected, and did give me cause to wonder, but having looked carefully through Olsen and Larsson I see it is well within range for Caspian - indeed pretty much a match for the juveniles they show. The white tips to the tertials and the scapular-covert white chevrons stood out and made the bird look very smart, and when it decided to be awkward and swim away from us, it only served to show off the white u/t coverts with a line of arrowheads [a bit blunt-tipped, maybe from the angle, but well-barbed and shafted] running up each side.

After reading this thread, I've had another look through 'Gulls...' and structurally, the closest match is easily plate 430 - if you allow for extra weathering [pic taken mid August] and the washed out effect of the light in that photo, the plumage is pretty much the same as well. Indeed, in both structure and plumage, the Blackhill Gull is closer to the Caspians on that page than anything else.

Coming away from the bird, I was happy it was Caspian [allowing for gonys paranoia]. I still am.

Ok, oar duly stuck.

Cristian Mihai · Jul 27, 2010

The neck band is rather a Caspian feature, but I'm still in the Yellow-legged camp. IMHO, there is no other strong Caspian feature in this bird.

Matt Prince · Jul 27, 2010

Thanks for the response Brian, Cristian etc. I remain unconvinced this is a 'clear cut' YLG - maybe I've been suckered in by the sloping head and bill. The dark underwing and dark eye patches do not, on reflection, look brilliant for CG.

I'm hoping the bird will hang around so I can go back - hopefully in flatter lighting.

marklhawkes · Jul 27, 2010

Agree. The bird in these photos is a 1cy Yellow-legged Gull.

Just picking-up on comments from Tom - when the Caspian was first reported, it was reported that a 1cy Yellow-legged Gull was present too. Could this be one of those (rare) instances where the "2 bird theory" actually might explain something?

Brian J Small · Jul 27, 2010

The Kerreran said:
::Enter, Stage Left, with large oar over shoulder::

Having spent an hour looking at the bird on Saturday, I have to admit I find myself rather surprised by these photos! The gull I saw had a VERY white underwing, for example, with only a little light marking; nothing like what is shown here. It's legs were markedly longer than anything else present, with a belly bulge behind them, and the head shape was pretty classic Caspian. The eye mask below and behind the eye, with a smudge on the ear coverts, is also fine for Caspian [their broader, more diffuse mask wears quickly, lasting longest around the eye]. Light grey-brown streaking on the crown but not the forehead also served to contrast the very black bill when the bird was head-on.

The bill was thicker than I expected, and did give me cause to wonder, but having looked carefully through Olsen and Larsson I see it is well within range for Caspian - indeed pretty much a match for the juveniles they show. The white tips to the tertials and the scapular-covert white chevrons stood out and made the bird look very smart, and when it decided to be awkward and swim away from us, it only served to show off the white u/t coverts with a line of arrowheads [a bit blunt-tipped, maybe from the angle, but well-barbed and shafted] running up each side.

After reading this thread, I've had another look through 'Gulls...' and structurally, the closest match is easily plate 430 - if you allow for extra weathering [pic taken mid August] and the washed out effect of the light in that photo, the plumage is pretty much the same as well. Indeed, in both structure and plumage, the Blackhill Gull is closer to the Caspians on that page than anything else.

Coming away from the bird, I was happy it was Caspian [allowing for gonys paranoia]. I still am.

Ok, oar duly stuck.

Hi Tom

Please don't take this the wrong way, but how many juvenile Caspian Gulls have you seen? In large gulls, experience is such a key element that comparing a bird with images in a book can sometimes lead to the wrong impression being gained.

Brian S

Marshall-78 · Jul 27, 2010

Brian J Small said:
Hi Tom

Don't take this the wrong way, but how many juvenile Caspian Gulls have you seen? In large gulls, experience is such a key element that sometimes comparing a bird with images in a book can sometimes lead to the wrong impression being gained.

Brian S

From looking at Tom's blog it would appear to be his first Caspian.

Steve Arlow · Jul 27, 2010

Having seen a few juvenile Caspian Gulls local to me in the UK, along with multitude of juvenile Yellow-legged Gulls, my initial impression on looking at this bird was of a michahellis. After looking at the images more closely I can understand why Caspian would be muted, slender bill, pale head, neck shawl etc however the over structure, tone and feel of the bird is of a YLG. I would not be able to turn this into a Caspian Gull if I had seen it locally.

The Kerreran · Jul 27, 2010

Brian J Small said:
Hi Tom

Please don't take this the wrong way, but how many juvenile Caspian Gulls have you seen? In large gulls, experience is such a key element that comparing a bird with images in a book can sometimes lead to the wrong impression being gained.

Brian S

Hi Brian,

Don't worry, no offence taken - in fact I agree with you. There is no substitute to seeing the things in the feather. And no, I haven't seen a definite Caspian before.
Having said that, I think books like 'Gulls...' are useful too, even with tricky immature larids, as they're written by people who really know the subject and use a lot of images which help to show the variation [though imho I think Mullarney's gull paintings are better than Larsson's..].

The point I was trying to make [perhaps with too much detail] was that photos can be misleading, and this is the case here. I've not seen any shots that make the gull appear as it did in life - I blame the location, not the photographers - and felt it was important to point this out.

Brian J Small · Jul 27, 2010

Tom

Keep on watching the gulls and things will fall into place.

If you PM me, I will try to get to you my and Chris Gibbins article on Caspian Gull from British Birds - I am sure I have a spare copy around here somewhere.

Brian S

Mole1 · Jul 27, 2010

Hi all

Thanks for your comments and for generating a bit of healthy debate. As for the 2 bird theory, I can not comment other than to say that I thought someone had seen the same bird on both Saturday and Monday.

I am happy that the bird I saw on the Monday is a YLG, so thank you for your confirmations.

JANJ · Jul 27, 2010

Classic Yellow-legged Gull, by the looks and for features mentioned by Brian.
Sexual dimorphism makes up for body and bill size - males are bigger with bigger bills.
Underwing is variable - both in Caspian and YLG, as in this YLG taken recently by Hans Larsson:

http://www.artportalen.se/artportalen/gallery/images/swe/birds/2010/large/228489.jpg

Caspian:

http://www.artportalen.se/artportalen/gallery/images/swe/birds/2010/large/228485.jpg

Note broader tailband less distinct white tips to tail, obviusly paler inner webb of inner primaries creating clearer 'window', like here:

http://www.artportalen.se/artportalen/gallery/images/swe/birds/2010/large/228482.jpg

http://www.artportalen.se/artportalen/gallery/images/swe/birds/2010/large/228067.jpg

'Giraff neck':

http://www.artportalen.se/artportalen/gallery/images/swe/birds/2010/large/228065.jpg

YLG:

http://www.pbase.com/slisch/image/126518619

Caspian:

http://www.pbase.com/slisch/image/126553613

A juvenile YLG as far north as Stockholm the other day:

http://blogbirder.blogspot.com/

JanJ

JANJ · Jul 27, 2010

I wouldn´t mind you sending me a copy Brian, haven´t in fact seen it!

B

JanJ

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