Wednesday, February 22, 2012

Caspian gull and cousins

A few days ago a fellow birder in Sudan identified a gull as yellow legged. This is apparently the first record of the species there.

At the time I wondered what the fuss was about. After all, my first edition of "Birds of the Middle East" says its common on all Arabian coasts in winter. And I found it difficult to believe that some wouldn't make the short trip over the Red Sea to the Sudanese coast. Indeed when I was in Jeddah in early November I saw a couple of medium-large gulls and identified them as yellow legged gull at the time.

However in the back of my mind I thought something wasn't adding up.

So to build on the dialogue about the Sudanese bird, I posted a picture, on BirdForum, of my gull from Jeddah.  Shock and horror, it turns out in all probability my gull is actually a Caspian gull.


Caspian gull seen in Jeddah, November 3rd

So what's going on? 

I now know what I should have known all along. There are three similar gulls - herring gull, yellow legged gull and Caspian gull.  Each gull dominates a geography. Herring gull dominates the north Atlantic, yellow legged gull the Mediterranean and Caspian gull  dominates the Caspian Sea and most of the Black Sea. 

Only in the south West Black Sea and northern tip of the Red Sea do Caspian gull and yellow legged gull vie for dominance. In winter there is dispersal and Caspian gull can be seen along all the Arabian coasts. Hence the reason my Caspian gull was in Jeddah.  (Just to add to the complexity - there is fourth similar bird called Steppe Gull found in winter on eastern Arabian coasts alongside Caspian gull).

So what went wrong for me?  

First, my Middle East bird guide is out of date. In the first edition of it, Caspian gull was still seen as a sub species of "yellow legged gull". Hence the comment in the guide book that yellow legged is found all along Arabian coasts. Furthermore the illustrations of the "yellow legged gull" in the book look like a compromise between the two birds.


Second, I was aware of the existence of Caspian gull from my second guide, the Collins guide to the birds of Britain and Europe. However I didn't investigate the Caspian option because the first guide said yellow legged gull was the one for Arabian coasts and the second guide says 75% of Caspian gulls don't have light eyes. Mine did - just like a yellow legged gull!

Now it all makes sense. The Jeddah bird is a lighter grey than a yellow legged gull and its legs aren't yellow enough. Its posture and bill are a perfect fit for a Caspian gull. It's in the right geographical location too. It just doesn't have dark eyes.  

In all probability, it's a light eyed Caspian gull and it's where it should be.


2 comments:

  1. However, your re-identification of these birds still raises the question of why no Caspian Gulls have ever crossed the Red Sea into Sudan. I think the answer is that nobody has ever looked and those that have looked in the past had exactly the same problem that you have had - that nobody knew how to identify these birds (and most still don't). The only thing I can hope to do is take lots of photos of gulls in Sudan and hope that experts on Birdforum can help me identify them.

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  2. Tom,

    I am sure you are right on all counts. I bet you will find plenty of Caspian gulls on the Sudanese coast and will be able to get the experts on BirdForum to do the IDs!

    Rob

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