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Caspian or Yellow-legged gull ... Kent, U.K. (1 Viewer)

Andy,

I am not suggesting that every odd gull is a hybrid, just keeping an open mind about a bird like this.
Yellow-legged Gulls have been pairing up with Lesser Black-backed Gulls and, to a lesser extent, Herring Gulls in the Netherlands yearly since 1987 and in Belgium since 1996. The hybrid offspring they produce also return to the colony when mature and produce backcrosses. Nowadays, about 10 YLGulls breed annually in the Netherlands, usually in mixed pairs. In Belgium, about 3 to 4 YLGulls interbreed, and about 10 hybrid gulls pair up with other gull species each year. Spain now has a small population of Lesser Black-backed Gulls too, and these birds regularly pair up with the local Yellow-legged Gulls. For instance, there were 17 mixed pairs on the Berlengas in 1996. I do not know the situation in France, but I do not see why it would be any different. Interbreeding is also going on in the UK, by the way.

Therefore, I think it is not too unreasonable to keep an open mind.
Also, I would plead for studying Yellow-legged Gulls not just on local patches but also in the breeding range, summer and winter. Maybe you have? I certainly have, and the OP bird looks a bit dodgy to my eyes - that is all I am saying.
I fully realise that the discussion is a bit pointless since the bird is not wearing a ring, so we can never be sure about its identity.
 
hi peter,

i was always wondering why hybrids (mich x tatus) have broader tertial and secondary crescents? broader than both parents? also, i have to confess that i have difficulties in seeing the differences. usually YLG have slightly narrower tertial crescents but these are minimal differences? same goes e.g. for the white primary tips which are also varying: YLG usually with smaller ones than herring but some have large tips too.
on balance, i agree that the OB here has enough oddities to be assumed a (possible) hybrid
 
I do not really know why, but the fact is that some hybrids (though far from all!) have rather wide white tertial and scapular crescents.
I agree that this is a subtle character, most useful perhaps in the colonies in spring, as the white tertial crescent of YLG appears to be more prone to wear and therefore becoming thinner then.
 
Andy,

Therefore, I think it is not too unreasonable to keep an open mind.
Also, I would plead for studying Yellow-legged Gulls not just on local patches but also in the breeding range, summer and winter. Maybe you have? I certainly have, and the OP bird looks a bit dodgy to my eyes - that is all I am saying.
I fully realise that the discussion is a bit pointless since the bird is not wearing a ring, so we can never be sure about its identity.

Thanks Peter. The stats are useful too.

Yeah, I can happily agree with what you (and Lou) have said.

I think you raise a good point regarding recording (images). This is something I should be doing, I reckon, on a website. Steve Arlow does this locally to a degree but other larophiles in SE England don't to a greater degree.

Whilst looking through the few images of gulls that I do have to hand at work, I found this image of a hybrid from winter 2006/07. Looks like many an Azorean! But it is a hybrid.

Note the leg colour on the LBBGs are dulled by the poor light/weather/camera.

Cheers,

Andy.

Edit: guess the leg colour of the hybrid - I'll post a pic showing the legs on monday :)
 

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OK, I headed down to the Thames today and had at least 30 Yellow-legged Gulls with most being immatures with just a few adults. A good count indeed. The weather was abysmal though and my digiscoped shots aren't great, but they do show that sub-adult YLGs often show dull yellow legs. Nice 1st winter YLG in the 1st shot too + three other YLGs. A bonus 1st win Casp last knockings was the icing on the cake.

Frustratingly, three of the YLGs had colour rings but they were too distant to be read.

Note the yellow legs of the adult Yellow-legged Gull and the adult LBBGs in the shots.

Cheers, Andy.
 

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Mick's bird was present again on the 30th November. Pic attached with a 3rd winter (fleshy-pink legged) LBBG alongside it.

Also another sub-adult male YLG present. Presumably a 3rd winter and also showing not particularly yellow legs.

Cheers, Andy.
 

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