cmichaell

Geoff,

First of all, agree its one of the smaller divers in non-breeding plumage. The relatively slender head, bill and neck rule out White-billed or very long shot Great Northern. In addition, both the larger divers usually have dark extending across the sides of the upper breast/lower throat whereas your bird is white here, with the black on the sides of the neck running straight back to the underwing and flank line. Very difficult to judge size on single bird but if flight style had relatively rapid wing beats, more like a grebe than a cormorant, then this would also support it not being one of the larger sp.

The clincher for the ID is the relatively narrow amount of dark to the top of the head and rear neck which indicates Red-throated. Both Pacific and Black-throated would show much more black here to around half the width of the neck whereas your bird appears to have dark confined to the rear third[=upper in flight] of the neck. Also the white appears to extend forward across the face . The eye is not discernible but the white appears to include the area where you expect the eye to be. This another feature in favour of Red-throated.

The bill isnt clear but some photos suggest possibly upturned with straighter upper mandible as Red-throated, compared to the more dagger-like bills of Pacific or Black-throateds which have both mandibles curved.

Another strong feature is the very white prominent rear flanks which appear to extend up towards the rump. This fits Red-throated and Black-throated but rules out Pacific. There is a suggestion of a dark vent strap, but that could fit all species.

At first impression, the upperparts appear to be quite black with strong demarcation and contrast to the white underparts, which suggests Black-throated, or to a slightly lesser extent Pacific, but this could just be the light conditions. On one photo the back and neck then appear  more brownish, which is what a Red-throated should be in good light.

Overall, a convincing Red-throated Diver and another bird to add to your ever-growing Po Toi list.

Mike