Wednesday 18 December 2019

Widening the Goalposts

Well, what a fascinating day it's been. Started work quite early to beat the weather, and a bit later in the morning virtually had to drive past Colyton WTW, so...

Just a quick look. Ten minutes. Fifteen, tops. Tsk! How is it possible to reach my age and still think you can kid yourself?! Chiffchaff heaven! After draining a camera battery and inserting a second I realised I probably should get on...

Via the estuary.

There were lots of gulls. By now it was blowing a hooly, and many birds were hunkered down on the islands above Coronation Corner. I went through them carefully, but drew a blank. Heading along the river I realised there was a good spread of birds all along, so drove to the bottom end and U-turned. First stop, opposite the tram sheds, and a gleaming white head shone across the river at me. Through bins I could see it wore a yellow ring on its gangly legs, and punted out a message on the patch WhatsApp group: 'Yellow-ringed prob Casp on estuary by tramsheds'. Why only 'prob' Casp? Well, I didn't need a scope to see it had much more heavily-marked underparts than I would like to see on a pure 1st-winter Caspian Gull. My ideal is white! A bit of flecking on the breast sides and flanks wouldn't concern me, but this bird had a lot more flecking than 'a bit'! I reached for the camera, dug out the scope and sallied forth...

First views were something like this. Even if 'gull' is a dirty word to you, I expect you can see what made me look twice. In my experience (which isn't vast, by the way) that sharply-demarcated white head is THE classic 1st-winter Caspian Gull feature to catch the eye.

I honestly don't think I've ever seen a more striking 1st-winter LWHG (sorry, Large White-Headed Gull - generic term). And just look at those stilts!


For me there are two main reasons why this isn't a classic, textbook 1st-winter Caspian Gull...
  1. The heavily-marked underparts. That grey on the belly and flanks is almost solid! The undertail area looks fine to me, but almost all the
  2. The strongly-marked inner greater coverts. I have seen chequered markings like that on Casp, but not as extensive. The outer greater coverts look better though, with a plain, dark base and pale tip.
However, having got home and loaded up the photos, I am finding myself a lot more optimistic about this bird. Why? Because everything else about it (that I was able to see) looked absolutely spot on. To me anyway. The structure looks perfect, the bill ditto. To my eye Caspian Gulls have a 'look' - basically a facial expression I guess - and this bird most definitely has it. The tertials and primaries look great. At one point it nearly blew over in a gust of wind, and I could see that it had a crisp, densely black tail band. Again, perfect. I never managed a proper underwing view, or decent open-wing photo. This was the best (the only) shot I got...

Interestingly, although the axillaries look rather strongly-marked, the underwing coverts that are visible look pleasingly pale...

Both the above photos are included just to illustrate the contrast vs typical 1st-winter Herring Gull. Chalk and cheese, aren't they? It's not a huge bird, and certainly not as brutish as some I've seen, so I'm guessing probably a female.

The yellow ring (X78C) indicates that the bird is from a German gull colony. On the ringing project's web page is the following note:

It is not possible to identify the ringed small chicks exactly... In most cases the gulls are Caspian Gulls or Herring Gulls, but note the existence of many hybrids. The participation of some Yellow-legged and Lesser Black-backed Gulls is also possible.

'Participation'. Hah!

So. The parentage of this striking beastie is evidently unknown. I await details of the history attached to this bird's ring, but am told it will probably come back as 'Caspian Gull'.

And then someone got me thinking...

A Twitter correspondant sent me a photo of a near-adult Caspian Gull in all its mature finery and quipped 'This is what it will look like when it gets older!' And a lovely 2nd-winter Casp - yellow X307 from the same colony. The point was clear. It might look a bit mucky right now, but when it grows up it will look exactly like a pukka Caspian Gull. And I believe he is correct. Structurally (and mostly, plumage-wise) I see nothing significantly wrong with it. Let's face it, a colourful family tree is nothing to be ashamed of...

Conclusion? I am going to widen those goalposts like the gull whore I am, and put it down as a Casp. I doubt the Devon Rarities Committee would be impressed though!

Finally. While crouched by my scope and staring intently at my camera screen, waiting patiently for the bird to fly, or open its wings or something, a chap strolled up and introduced himself, whereupon I pointed out the gull. In case he reads this, I would like to apologise to Mark for focusing so rudely on my camera throughout. It was very nice to meet you by the way!

Which reminds me. Crouching! Aaagh!! I am getting too old for prolonged crouching...


  1. Hi Gav - very interesting bird. As you know I only have a very limited experience of Casps, and I know they show tremendous variation, but I think the grey underparts, solid grey shawl (not spotted) and greater covert pattern point quite strongly to some Herring Gull gene influence, which I think is quite prevalent in the German colonies. If you can get hold of Rich Bonser on twitter I'm sure he could offer more insight. Would love to have seen it and look forward to hearing what others think. All the best. Matt

    1. Hi Matt, yes, it's a bit of a stunner isn't it?! I haven't had ring details back yet, but it's certainly from a German colony where hybridisation occurs. If it didn't look so good structurally I would just let it go as a hybrid, and likewise if more of the plumage was off. But for some reason I really like it, even if (as seems likely) there's been some inter-species hanky-panky somewhere in its ancestry. I shall see if I can get some opinions from London birders though, that's a good idea. Cheers.

  2. Hi Gav, I think you are very restrained here. Just look at your bird without the minutiae. If you look at a field of juv fw Herring Gulls there are scarcely two the same, and this goes for all large gulls so why would there not be some variation in Capsians? With large gulls I think it is wrong to home in on an idealised version. Even in a 100% Caspian Gull colony I bey only 50% would fit your vision. Get it in the book - Caspian Gull 1. :)

    1. Good point re Herring Gull variability Stewart, I hadn't previously considered applying that to Casp, but yes, I don't see why not. As I mention in my reply to Matt, it's the structure that appeals to me with this bird. It simply looks like a Casp to my eye, and the less-than-ideal plumage features don't worry me as much as they would if it had a Herring Gull's head, say. I used to have the BB edition with the Gibbins et al Casp ID paper which suggests a scoring system for various ID criteria. I'd be interested to see how it fared in that.

      It's in the book Stewart, and I don't think anyone is going to be able to talk me out of it!