Caspian

There’s been a Caspian Gull at Sheringham for some months. Before the lockdown Tania and I walked along the prom to try and find it and got talking about the features of identification; how to distinguish an immature Caspian Gull from an immature Herring Gull. As we stood above a gathering of gulls on the beach I explained structure is key.

“A snouty appearance with long legs. Couple this with a pale head and a white rump and darker distal end tail feathers”. Are all good starting points.

Friend Bob’s photo on the front cover of the latest Norfolk Bird and Mammal Report is an excellent reference. We stared through the gulls and as if by magic it was there. Preoccupied in discussion we didn’t see it fly in!

Gullfest

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Some great gulls around the pier in Cromer at the beginning of September. This 1^st year Caspian Gull and an Adult Yellow legged Gull keeping the Larophiles entertained. 

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There was also an adult gull showing characteristics of a Caspian. When we attracted the bird close with a little bread the seemingly dark eye turned pale. The lack of a prominent tertial step was perhaps because the bird had a moult worthy of a bald dog. Others were also seeing a ‘snouty’ appearance as well as long legs. I couldn’t really see this but tried hard to see what they meant. The gull ‘morphed’ every time I looked at it. I eventually got a series of shots that showed sufficient detail to convey the shape and size of the bird. It started to look more likely there was some Caspian in it … but I couldn’t be sure. The upshot was I didn’t know.

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I have been referring to the paper on ‘Identification of Caspian Gull’ by Chris Gibbins et al. which states that ‘non calling birds  can be identified using head and bill shape alone (call and calling posture are diagnostic – but this bird remained silent): other structural features vary and so are less important’

To be fair the bird in the above photo of it running looks long legged and snouty with a parallel sided bill so I guess on that basis alone it’s a Caspian. Other photos  however show it with a rounded head. I just couldn’t help feeling it’s not so straight forward and I couldn’t make up my mind. The books weren’t enough. I wanted someone with much more experience than I to take a look.  Via Mark Golly, Chris Gibbins, who is currently in Georgia, has commented as follows:

“Plenty of birds here just like this in fact.  I appreciate your point – its not the minds-eye image of cach, but I can find many birds (I’m guessing females) that really are like this structurally. The pale eye is of course not entirely unprecedented in casp but I can see why in combination with the jizz it gives you trouble.  This type of more rounded head is something I see frequently; but if you look at the structure of the bill it is really good for Casp.  Many at the moment have this light head streaking which, as with mich, soon wears off. The moult and wear dont help in assessment of primary pattern, but the P10 tongue seems long, square ended and whitish – paler also than the upperparts.  So seems fine. Black just on outer web of P4 is fine.  Leg colour is also no problem for me.”

“I think it really is a case that when you are a saddo like me and looked at many many casps, this bird is not out of range of acceptability.  BUT it really would be worth throwing bread out to get birds fighting, and listen out for its call.  With some birds this really is the only way. I will look again properly at the pics once I’m back and give you a second mail but my first impression is that it is actually OK.”

My thanks go to Chris and Mark Golley for their comments and to Simon Chiddick for finding the bird. 

It boils down to experience. I was certainly being too conservative. If it had looked like a bird I saw at Cley the other month I would not have thought anything but Caspian… no doubt about that one!

Now where’s that bread?

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