Sunday 17 September 2017

Yes You Guessed It - More Caspian Gull Stuff

It's been a great couple of months for enjoying the young Caspian Gulls at Shawell. These are the vanguard of a major range expansion of this species. Herring Gulls need to watch out or they will find themselves pushed out.

A juvenile Caspian Gull was a major prize a few years ago, but now you could reasonably expect to see one anywhere gulls gather in large numbers in England. Of course you need to have done your work to understand how to identify them.

The window of opportunity is quite tight, as they begin moulting almost as soon as they have made it here. In fact most have replaced a few scapulars by the first or second week of August. By mid-September some are in almost complete first-winter plumage. This is one of the ways of helping to distinguish Caspian and Yellow-legged Gulls from Herring and Lesser Black-backed Gulls in their first few months. However, by mid-September quite a few of them are moulting too although they still look fresher. Caspian and Yellow-legged Gulls are born about a month earlier than the other two.

A Juvenile Caspian Gull's plumage is quite dull. The one below is typical of what to look for: very little patterning on the greater coverts (GC from now on). The inner GC are plain dull brown and the outer GC are a mixture of off white and brown. The darker inner GC often appear similar to the Nike swoosh logo. The median coverts (MC) and the lesser coverts (LC) are plain brown with buffish edges (if you don't know the feather tracts I'm talking about just enjoy the pictures). Of course the small head, long legs and the long winged appearance all help.

Juvenile Caspian Gull, Shawell, August 10th 2017

The one below shares all the feature of the one above and has a real dagger of a bill. Caspian Gulls love to just sit about.

Juvenile Caspian Gull, Shawell, August 12th 2017

The next one was quite distant, but you can still see the general plumage features and the washed out brown colour really shows well in this image. The whiteness of the head is a helpful although only when seen in conjunction with the rest of the features. The hanging rear belly is another feature of Caspian Gull, but it's not always like that and they can lose it two seconds after you see it.

Juvenile Caspian Gull, Shawell, August 24th 2017

By early September some of the scapular feathers have been replaced and a greyness starts to appear. The coverts still show that plain dull brown colouration.

Moulting Juvenile Caspian Gull, Shawell, September 9th 2017

You can clearly see the replaced scapulars on the next one

Moulting Juvenile Caspian Gull, Shawell, September 16th 2017

The next two images are of a German ringed bird X454. This one is a little trickier because it often looks a little short legged and dumpy. Not all the time though and care has to be taken with judging Caspian Gulls jizz, as they are very good at being shape changers. As you can see it has already moulted some of its median and lesser coverts, which is very good Caspian Gull pro feature. Its juvenile coverts are all OK, as are its tertials. I will give it the benefit of the doubt, but with the proviso that we watch it develop - good things these colour rings. Not all Caspian Gulls are sleek with a long straight bill and super long legs.

First-Winter Caspian Gull, Shawell, September 16th (X454)
First-Winter Caspian Gull, Shawell, September 16th (X454)

X739 is a smart looking bird although my photo hardly does it justice. As you can see this one has moulted its scapulars, but none of its coverts yet.

First-Winter Caspian Gull, Shawell, September 14th (X739)

The next one a first-winter has moulted its mantle and scapular feathers plus a few median coverts and is the most advance one I've seen so far.

First-Winter Caspian Gull, Shawell, September 16th

The last one X735 is a stinker. If you look closely its greater coverts are chequered and its jizz is more like that of a Herring Gull. Also the size of the markings on its scapulars are a little too bold. I might be doing it an injustice, but I think its a hybrid HG X CG. Its colour ring is not visible but it is the one with its head up.

First-Winter Hybrid, Shawell, September 16th (X735)

1 comment:

  1. Great insight into Caspian Gulls mate keep up the good work!!