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Dark-rumped Swift at Doi Lang, Thailand. (1 Viewer)
- Thread starter noble-lite
- Start date
I believe this is a vagrant to Thailand, so should be treated with caution. If it was Pacific or Cook's, we should be able to see the sides of the white rump even in profile, and the underparts are heavily scaled, so you may be right. It would be a good idea to seek an opinion from someone with experience of the species, however.
I've never seen this species, but the unbarred black undertail coverts are supposedly a very good feature for Dark-rumped and can clearly be seen here.
James Eaton
Trent Valley Crew
From that photo, I can't see why it would not be a Cook's Swift:
https://macaulaylibrary.org/asset/197846871
https://macaulaylibrary.org/asset/61142151
https://macaulaylibrary.org/asset/90947931
A photo showing the upperparts would be required to prove otherwise.
James
https://macaulaylibrary.org/asset/197846871
https://macaulaylibrary.org/asset/61142151
https://macaulaylibrary.org/asset/90947931
A photo showing the upperparts would be required to prove otherwise.
James
noble-lite
Well-known member
Thanks for all those comments guys.
Is this the only image you have?
I think James is right in that we don't have a profile view here. The white rump on Pacific/Cook's wraps around a bit, so can be seen in side profile, but not from a view like this.
Andrew, I have a feeling that solid black undertail-coverts are common to all the species of Fork-tailed Swift except perhaps for Blyth's, but I may be wrong.
I think James is right in that we don't have a profile view here. The white rump on Pacific/Cook's wraps around a bit, so can be seen in side profile, but not from a view like this.
Andrew, I have a feeling that solid black undertail-coverts are common to all the species of Fork-tailed Swift except perhaps for Blyth's, but I may be wrong.
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I'm only going on what it says in the Lynx guide to Thailand, where it does mention the solid black undertail coverts of Dark-rumped as distinctive from Pacific and Cook's. The illustrations in the book show this quite well. From James's photos it seems that the pale barring can be hard to see on Cook's, although it's present. There's no trace in the OP's photo but that may be an effect of the quality of the photo.
noble-lite
Well-known member
There is only the one image, regrettably, but what you all say is very informative. We certainly did see Cook's Swifts in the same area on three consecutive days. It's only when you review images that things get interesting.
noble-lite
Well-known member
Thanks guys. We have actually had some input from a co-author of the Lynx book, who says - The narrow white rump-patches of Cook's can sometimes be incredibly hard to see in the field. Throat colour is ok for Cook's (though the recent article in latest BirdingASIA has demonstrated how similar pale throat Dark-rumped can have). The very narrow pale fringes to undertail-coverts can also be hard to see, unless the bird is really close. There have been various independent attempts to observe Dark-rumped Swift and photograph it, but there has not been a confirmed record since the specimen collected in the old days.
From this angle, the only indicative feature to separate the two to me is the white scaling on belly. I think the scaling is too narrow to be a Dark-rumped. It looks like a perfect Cook's to me.'
From this angle, the only indicative feature to separate the two to me is the white scaling on belly. I think the scaling is too narrow to be a Dark-rumped. It looks like a perfect Cook's to me.'
noble-lite
Well-known member
Thanks guys. We have actually had some input from a co-author of the Lynx book, who says - The narrow white rump-patches of Cook's can sometimes be incredibly hard to see in the field. Throat colour is ok for Cook's (though the recent article in latest BirdingASIA has demonstrated how similar pale throat Dark-rumped can have). The very narrow pale fringes to undertail-coverts can also be hard to see, unless the bird is really close. There have been various independent attempts to observe Dark-rumped Swift and photograph it, but there has not been a confirmed record since the specimen collected in the old days.
From this angle, the only indicative feature to separate the two to me is the white scaling on belly. I think the scaling is too narrow to be a Dark-rumped. It looks like a perfect Cook's to me.'
From this angle, the only indicative feature to separate the two to me is the white scaling on belly. I think the scaling is too narrow to be a Dark-rumped. It looks like a perfect Cook's to me.'
