Caspian Gull – hybrid?

One to learn from

Sometimes the most educational birds are also not straightforward to identify. Found this bird couple of days ago. Up to 250 large gull  gathered by mid afternoon on metal roofs, some bathing in the River Don. Many northern ‘argentatus’ Herring Gulls, fewer GBB Gulls and a handful of Lesser Black-backs. From a distance it had a good look of Caspian about it. A large bird, longer-winged and more upright in stance. The head looked small in comparison with body and rather thinner bill. Main feature in conjunction with structural elements was a spotted look to the immature upperparts. There is ‘something’ about Caspian in the spotted character, especially on some 2nd winter types. Hard to explain exactly  why.

So drove closer.  A little less impressive closer up. The legs rather short and bright and the underparts also had bit more streaking below than you would ideally want. Not a ‘slam-dunk’ 2nd winter Caspian then.

Feeling a little rusty I contacted some Caspian-loving friends. All concurred, not confident it’s a pure bird – perhaps argentatus X cachinanns hybrid.

Caspian features I see:

The head and bill looks good, white-headed, rather slender (for size) parallel-sided bill with darkish tip and lovely dark line bleeding back towards bill base. White head nestled in coarse lower nape streaking.

Upperparts ‘spotting’ ; mix of grey feathering with cream tipped , darker spotted feathers, couple of adult grey median coverts. tertials solid dark centre apart from ‘adult grey’ smaller, upper tertial(s) – the latter a classic Caspian combo, rather longer blackish primaries (but no pale mirror on p10- very common on 2nd winter Caspian).

Here it is – see what you think. Not great photos- flew off in large group shortly after- no chance to see tail pattern and underwings. Not present yesterday. Caspian Gulls are RARE in Yorkshire- so we need to get them right…

With thanks to Brian S, Ian Lew, Nic H and Chris G for keeping me on the right track!

2 thoughts on “Caspian Gull – hybrid?

  1. Jan Jörgensen (JanJ)

    Hi Martin.

    As you have already guessed, it´s not a pure Caspian (type like this:
    http://www.elisanet.fi/hj.koskinen/2cyCaspian_Tara20091113.html or this:
    http://www.elisanet.fi/hj.koskinen/2cyCaspian_Tara20091108.html, note a remote plumage similarity to your bird in the last finnish bird. I´m not even sure it´s a hybrid. but I would not argue wholy against that. I see more of a washed out 2 cycle argenteus (pale greytone). Herring, both structurally and plumage wise, not to mention the short strurdy legs. Bill seems also to be on the short end for Caspian.
    In the third pic it shows somehow a slight Caspian structure around the head and pushed up breast.. I´m not sure of how a 2 cycle argentatus x cachinnans relly would look like.

    JanJ

    Reply
  2. Caspian

    An intriguing discussion is definitely worth comment. I believe that you need to write more on this issue, it might not be a taboo subject but usually people don’t discuss such subjects. To the next! All the best!!

    Reply

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