wgeoff

A Diver flew past my seawatching station on Po Toi yesterday (Wednesday 27th) at 4.30pm. I think this is the same bird I saw two weeks ago. Here are six real size photos and three enlargements x2.



I think this is a small Diver but not a Red-throated because of the dark colouration of the upper wings and back, and the size of the feet extension. Between Black-throated and Pacific, I'm not sure, but some features such as the peaked head and white flanks may suggest Black-throated.

Expert's help please.

[ Last edited by wgeoff at 18/08/2010 17:52 ]

Hendrix

Yellow-billed Loon ?

kmatthew

I vote for Black-Throated as well Geoff, same reason as you.

ajohn

I don't claim to be an expert on diver ID, but my feeling is that this is a red-throated for the following reasons:

Head and bill look comparatively small and neck fairly slender
Bill appears slightly up-tilted (although this is difficult to judge on a long-range shot!)
Extensive white on the sides of the neck, with only a narrow band of black down the back of the neck
Extensive white on the rear flanks, coming high onto the sides of the body

wgeoff

Thanks for these responses.

After a review of the photos and a few books, I think John has it right, especially the first three points he makes, which are more reliable pointers to the id than mine.

So I think Red-throated Diver is the correct ID.

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

wgeoff

Thanks Mike for this very detailed and helpful analysis of Diver ID. The bird looked very black and white when I first saw it, but I agree this can be just a light effect, especially over the sea.

In these situations, you only have a few seconds to look at the bird (I can estimate very accurately from the timings on my photos, the bird took less than 10 seconds to pass me from the time I first spotted it). You have to make the choice between watching the bird or using the camera, there is no time to do both. I guess if I had used this time to just watch the bird, I may have seen the upturned bill. But now I always choose to use the camera as a more reliable and permanent record.

You can see nothing of the features through the camera viewfinder at this range, so it is a risk. But the resulting photos almost always justify the choice, particularly when other more experienced observers can comment on an image and not just a written word.