A Tricky Caspian Gull

On January 20th I found a gull at Shawell A5 Lagoons, which I initially identified as a Caspian Gull, but I was concerned that its mantle was a bit too dark and that it still had many juvenile feathers. The series of photographs below, show most of the features and as you can see the mantle looks darker than shown by typical Caspian Gulls of this age and at this time of year. It is really interesting to see that it still has some juvenile rear scapulars and all the greater coverts are first generation. This is not typical for a first-winter Caspian Gull in January. I considered Heughlin's Gull, but I couldn't make a strong case for that as on the upperwing there is a pale area on the inner primaries, which Heughlin's shouldn't really show and the underwings are very pale.

First-winter Caspian Gull, Shawell A5 Lagoons

I placed images of this gull on Facebook's UKGulls, asking for opinions and I wasn't the only one to give thought to the possibility of it being a Heughlin's Gull. Many comments on there agreed with my initial identification of it being a Caspian Gull, but not everyone picked up on the fact that it still had many juvenile feathers.

I asked a chap from north of the border who has bucket loads of experience with Caspian Gulls  and he said 'Looks like a Casp, although strange to see a bird with so many retained juv scaps'.

On Facebook Peter Adriaens said 'A quick check among my photos of 1c Caspian Gulls from January reveals about 30 birds with a few retained juvenile rear scapulars, so it is not that unusual. Latest one with retained juvenile scapular was on 1st of May. In any case, with such a pale, whitish underside to the hand, I think there can be little doubt that this Leicestershire bird is a Caspian Gull. The underside of the primaries is rather dull blackish-brown in 1c heuglini'.

I am happy that it is a first-winter Caspian Gull, but an interesting and smart looking one. Learning the parameters of acceptability for this species is a great learning curve and one that I am really enjoying.

First-winter Caspian Gull, Shawell A5 Lagoons

Very White Underwing Pro-Caspian Feature

First-winter Caspian Gull, Shawell A5 Lagoons

First-winter Caspian Gull, Shawell A5 Lagoons

First-winter Caspian Gull, Shawell A5 Lagoons