In the quiet summer period I've been looking at Cormorants again. The more I look at, the more interesting I'm finding them. The gular angle seems to be the key to identifying them racially, with almost all of the other features being variable. The two birds in the first two images below are siniensis at the back and carbo at the front. The gular angle makes this obvious, however the structure of these birds isn't such a big help as they should, in theory, be the other way around!
Structurally, the carbo should be the thicker-set bird, with the flatter crown. and more stocky bill. However this is presumably a male siniensis, and a female carbo, making looking solely at structure, in this case, not useful.
I've moved the heads of these birds in Photoshop so the gular angle is more obvious. (Castle Mills GP, Beds, 24th July 2009)
The birds below are carbo on the left, and siniensis on the right. Both are immatures and their white underparts are noticably different, with the gleaming white belly of the siniensis bird really obvious. (Marston Vale CP, Beds, 1st August 2009)
A bit more on this pair can be found here.
No comments:
Post a Comment