Wednesday, 7 March 2012

Sub-species Interest

When there's not a lot going on locally on the birding front one naturally tries to find interest where one can and this is where sub-species can come in. In fact I think that there is a strong case for counting sub-species on one's various lists. After all, since listing is ultimately completely pointless and a totally personal thing then why not county everything that you can identify? Of course if you are going to want to compare lists with others then you need a set of rules but since I have no interest in that at all I'm considering converting to a "all sub-species" list. Think about it: American black tern, Azorean yellow-legged gull, blue-headed wagtail, channel wagtail, Taiga & Tundra bean geese, pale and dark-bellied brent, black brant, suddenly there's a whole lot more stuff to go for. Gradually many of these birds are being granted full species status anyway but if you're just listing for yourself then there's nothing to stop you taking the plunge early and converting to the "anything goes" listing approach! At the very least I keep note of the various sub-species that I've seen though they're not (yet) on my headline life list tally.

Anyway, I was reading Gavin Haig's excellent blog "Not Quite Scilly" and he was going on about how to identify sinensis (Continental) cormorants. Whilst I have periodically read about people picking out these birds I had only the vaguest of ideas what the diagnostic criteria were so it was most useful to have it explained. For those who don't know it's to do with the angle that is made by the gular pouch, the (often yellowish) area at the base of the bill.

A helpful diagram copied second-hand from Newson et al.
"Subspecific differentiation and distribution of
Great Cormorants Phalacrocorax carbo
in Europe". Ardea 92(1): 3-10.

Now cormorant is not a bird that I photograph very often - let's face it they're just not that attractive but having learnt a new bit of bird ID I searched around for something to try it on and remembered a photo that I'd taken and blogged a few weeks ago of a cormorant in a side stream on my local patch at Port Meadow. Here it is again for those who missed it.

The Port Meadow bird (click to enlarge).
There's no arguing about the gular
patch angle here, clearly a sinensis

Here's a photo that I borrowed from Gavin's blog (c) Gavin Haig.
Note the much more acute angle of the gular pouch
so it's a home-grown carbo.

Result! Clearly a sinensis cormorant on the local patch. Now, I don't think that they're that rare in Oxon but I wondering whether anyone has bothered to take a look through county cormorants to see how many of them there are. Perhaps no one actually cares but it gives one something to check on even the commonest and arguably one of the least attractive of birds. Whilst waiting for the next good bird, having something to check on common species is not something to turn one's nose up at.

Talking of sub-species I'd just like to slip a cheeky gull into this post. I spotted it at the weekend whilst on a brief walk with my five year old son in tow so it was bins only and I'd get grief from Luke if I stopped for too long. I managed to snatch a photo of this fine intermedius lesser black-backed gull, which is basically the Scandinavian equivalent of our home-grown graellsii. Of course the much more sought after LBbG sub-species is the fuscus or Baltic gull which lives further east and is almost black with a ridiculously long primary projection.

Nice intermedius. Note the much darker colour mantle colour.

...and here's a reminder of the Appleford fuscus Baltic gull
(Ian Lewington certified) from October 2009 that I
was lucky enough to jam in on whilst not seeing the
Azorean gull. Note the unfeasibly long primary
projection and the almost black mantle colour.

So there you have it, sub-species offer you something of interest to do whilst waiting for the next good bird. Clearly my nerdiness knows no limits and I think that I can hear my VLW weeping quietly into her tea in the kitchen.

It turns out (thanks to Ian Lewington) than in Oxon sinensis is now the common cormorant, having mostly replaced the carbo's. That's fired me up to go and try to find a local carbo for myself. See how interesting sub-species can be!

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