[Tropicbirds] Immature Tropicbird sp. 鸏

Having finally cleared family duties I've had a few minutes to look into this and must say that I strongly agree with Mike Leven's views on this bird.

Roberson's material seems much more authoritative than the Indian field guides - tropicbirds are definitely NOT Pamela Rasmussen's first love and when you look at the text it is rather thin, simplistic and in places odd - talking for example of a 'short rounded' tail in Red-tailed, which is not borne out in the plates (having said that though I think her text still favours id as Red-tailed).

The bill of this bird in my view most closely resembles that of Red-tailed, and in no way resembles that of White-tailed - see Roberson's photos of actual specimens.

Moreover, Roberson states:

Upperwing patterns are diagnostic. At all ages (my emboldening), Red-tailed Tropicbird has virtually all-white remiges (primaries and secondaries) so they look essentially "white-winged" in the field. This works both on quite young birds  and older individuals up through adults. This is easy! ...the outer primaries on some Red-tails have black shaft streaks, and some tertials have black centers, but these are very fine points. All Red-tails appear essentially white-winged in the field."

This bird was thickset in my view, resembling a booby when it first landed on the sea at great distance, then, after I'd called it as tropicbird, making me think I'd lost it and picked up an egret so white-winged was it.

I think it very closely resembles the photo at the end of Roberson's paper which he identifies as an immature Red-tailed of around 30 months, which one would apparently expect to assume full adult plumage in a further 12 months.

It's late now, and I just lost a first version of this, so I hope it makes a little sense - and of course we will need to refer these images to overseas experts, I think, to get a definitive id.

Mike Turnbull


I contacted Don Roberson, and he has responded immediately, but only after a couple of hours of careful examination of our and his own photos that he believes this is indeed, juvenile White-tailed.

I shall post his reasons in full this evening, but essentially the amount of dark webbing on the outermost primary, which always seemed problematical, is crucial.To quote Don:

... Gould, King & Sanger (1974) describe the outer remiges of juvenal-plumaged Red-tails as having "a black suffusion spreading into the vanes, both dorsally and ventrally, the the black dorsal shafts of the larger primaries, EXCLUDING THE OUTERMOST" (my emphasis). That means that the outer primary should be all-white even on juvenal Red-tails. Only the shaft is dark. On my flight shot of the juvenal Red-tailed below, which I've blown up and lightened and added contrast, you can see that the outer primary is all white and that the dark suffusion onto the vanes is interior to that, on penultimate remiges. On the close side view, only the shafts look dark.

The Hong Kong bird clearly has an entirely black outer web of the outermost 2 primaries; and some black on the outer web of P8 and a spot on the outer web of P7. None of these black outer webs reach the tip of the feather, which is white. This is a White-tailed pattern; I found a shot on line from the eastern U.S. -- in the Atlantic -- that is fairly similar at
except that it has more black on P8 and P7 than the Hong Kong bird. But presumably the races are different?"

I shall post Don's photos once I have his permission to.

Mike Turnbull


This point about the fore-webbing of the outermost primary always being black in White-tailed but never in Red-tailed is the main reason we believe our bird to have been White-tailed - the flight photos obtained have helped immensely.

Dr Dunlop's input is nevertheless gratefully received corroboration.

To my mind our bird still has a bigger bill than the birds in Dr Dunlop's photos.

I wonder therefore how useful impressions of bill size actually are.

Mike Turnbull