Ringstone Edge

Continental Cormorant, P c sinensis.

'European Birds' by Hume et al (Princeton University Press) explains how the shape of the yellow gular skin usually tells which subspecies a bird belongs to. This skin is pointed on P c carbo, and squarer on most P c sinensis.

This is because of the angle between the gape and the rear edge of the gular skin. For this angle the ranges given are: carbo 30-72 degrees, sinensis 66-111 degrees. (A few birds in and around the overlap zone cannot be assigned to subspecies.)

PS: I've had a response from the BTO about the Canada Goose with a neckband seen two days ago. It is not one of the Norfolk birds. I've now been asked to send my photos to someone at WWT Slimbridge.