2nd cy gull

[Jörgen Bernsmo]

What do you all think of this one? Seen today at Simrishamn SE Sweden.

[Theo Muusse]

Hybrid micha x cach or tatus.

Theo

[grzegorzneubauer]

I agree with Theo
G.

[JanJ]

Agree with the two above. Good quality pic from Jörgen as usual!

JanJ

[Jörgen Bernsmo]

I think argentatus is involved and my guess would be tatus x cach. Albeit not as cach-like as most presumed hybrids of this combination that I´ve seen. The pattern of the underwing and tail in favour for tatus being involved-in my opinion. The inner hand did seem to fit michahellis well with only a faint window but I guess a hybrid tatus x cach could look that way too. I don´t know how likely it is with such advanced moult in cach x tatus and the rather short-legged and stocky jizz is due to abraded or broken p9-10 that in flight looked shorter than p8. First reaction in the field was michahellis due to the moult pattern but looking closer the tatus x cach combination seemed more likely with tatus carachters dominating. In some angles the head looked cach-like with parallel (but too short) bill.
I guess G Neubauer is the one with best field experience of known hybrids and pointers to why this should be a micha x cach or tatus would be appreceated

/Jörgen

[JanJ]

I think that Jörgen probably has anwered his own question. But then again - a possible involment of michahellis - could that be excluded?
The first impression when seeing this gull was somewhere around cachinnans x argentatus. If michahellis genes are involved would it be possible to detect signs of that? I doubt it. So, we can probably expect some further suggestions from Greg...

JanJ

[lou bertalan]

hi jörgen, all,

plumagewise i find nothing that is wrong for a caspian of this age. it's the structure (short bill on a massive head and rather herring like line of breast and belly, apparent compactness and shortish legs) that is odd and suggests tatus as a parent or grandparent.
why i say there is nothing wrong with plumage: the rather fine contrasting transversal bars on tail (towards base), and 2nd gen. TT, inner GC and MC are rather typical for caspian gull! head striation is acceptable, smudge around eye reminds of mich but is not unseen in cachinnans. tatus x cach is an (increasingly?) common hybrid type while i still have no images of definite documented hybrids mich x cach (although i know they have occured in poland) but probably are one of the rarest combinations in european large gull hybrids. like jan i see no suggestion of michahellis in this bird except maybe for the large head. just to add: venetian blind in "window" is a rather variable character in both michs and cachs, with darker cachs often having less pale inner webs as one would like to see in a caspian while many michs have extensively pale inner webs (esp. eastern birds).

regards,

lou

[grzegorzneubauer]

Hi,

[cannot quote selectively...]

lou writes:
"while i still have no images of definite documented hybrids mich x cach (although i know they have occured in poland) but probably are one of the rarest combinations in european large gull hybrids"

there is one photo of cach x mich published in DB 32, 2010: plate 216 and I have another one extremely similar bird photographed from Krakow (non-ringed, unfortunately). But, yes this type of hybrid seems to be rare due to limited overlap of breeding ranges (from the other hand, hardly any research was conducted on breeding gulls in the 'zone' of possible overlap - Slovakia? Hungary? Czech Rep? etc. - apart from PL). I'm unable to exclude any mich influence, there is too few data on known hybrids still.
Concerning the rest and assuming that it would be cach as Lou suggests: my impression is that darker birds are darker overall. Eg, if there are rather well-brown axillaries like here, than also 2nd gen mantle-scaps should be darker (by eg large, dark diamond-shaped centres etc). In other words there is usually correlation in darkness of different parts of plumage (to be described...). This is not true here: the bird is very pale on the back with general whitish background and relatively thin barring on scaps. While such a distinct barring may perhaps rarely occur in cach (but no such cases with this on ringed birds from Ukraine in my library!). I also wonder is this dense brown barring on uppertail covs/rump is OK for a cach.
Still think a better guess than atypical cach is an option of cach x tatus hybrid.
G.

[adriaens]

Perhaps I am overlooking a few obvious things, but I am wondering why everyone seems so sure that this is not a Yellow-legged Gull ?
Pale rufous-brown juvenile wing coverts are certainly possible, and the tail and rump pattern are still within the variation.
Here is a recent one from southern France, with similar markings on tail and rump:

[JanJ]

Another one by Steve Arlow.

JanJ