There don't seem to be any accurate depictations Bannerman's Shearwater Puffinus (bailloni) bannermani in any guides I've seen and if you google it there's doesn't seem to be a huge amount of concrete information on-line either. Prior to seeing them on the recent trip to the Iwo Islands I wasn't even able to have complete confidence in some on-line images labeled as such, in part due to differing taxonomic interpretations. Now that the newly recognised Bryan's Shearwater P.bryani is believed to breed in the Ogasawaras there's even more reason to look at small shearwaters there carefully.
Having the good fortune to see about 25 Bannerman's in just a couple of days, at varying distances, angles and light conditions provided a wonderful opportunity to get to grips with how they look. I wanted to photograph as many as possible regardless of distance and managed to record 18 small shearwaters, not surprisingly the quality of these hand-held efforts ranges from not too bad to downright awful. Interestingly however, I feel that even the distant blurry specks are recognisable as Bannerman's which are more distinctive than I'd anticipated.
The images I'm posting are cropped to the same degree to reflect the varied distances and I've kept sharpening to a minimum, if at all, to avoid unwanted side effects. This has the benefit of imparting a sense of field conditions. I looked at all the closer birds through binoculars before trying to get any photographs resulting in a greater proportion of flying away shots while just dashing off record shots of more distant birds.
Setting aside the uncertain taxonomy, there are images of 15 Bannerman's plus two other birds which I think could be Newell's P.newelli and Tropical P.bailloni respectively. Both would be great rarities in Japan however as there are very few opportunities for birders to reach these waters over 1,200km south of Tokyo there is a real possibility that they, and other seabirds, could be (seriously?) under-recorded. There wasn't so much as a sniff of hoped for Bryan's.
Below is a useful series of three images of a single bird, showing it approaching, side-on and flying away, which shows Bannerman's features to good effect.
BIRD 1 (three images). A typical individual, at all angles and light conditions the greyish hind neck is conspicuously paler than the tail and undertail coverts.
Pale fore and dark aft, note the white spot in the tail (toes?), it may be hard to see in the field but can be surprisingly obvious in photographs. The neck always looks greyish but the pattern and extent of white and grey is variable; some have a more extensive shoulder mark on the breast side and on some white intrudes up behind and even round the ear coverts reaching as far as the eye. Birds with extensive white and greyer crown can have dark brown restricted to a distinct dark mask. Perhaps this could be age related? The underwing pattern seems constant, the hand with white greater primary coverts, piano key medians and dark lesser and marginals. The dark primary bases contrast strongly with the white centre of the wing. The arm is white with a brown bar on the lesser coverts, dark secondaries form a broad trailing edge in contrast to dark marginals creating a very narrow dark leading edge It has a longish bill with a heavy-looking tip.
The vent has a very sharp division between blackish and white, the 'tail spot' is still visible here.
BIRD 2 (one image). A carbon copy of the previous bird at greater distance.
BIRD 3 (one image). The grey neck looks paler here and there's a distinct white intrusion above the ear coverts producing a bold masked appearance. The tail spot is just visible at this range. Bannerman's often has something of a pterodroma feel, the underparts markings and the proportions.
The following is a series of five different birds showing mainly the underparts at a distance. Having seen the appearance at closer range it isn't difficult to make out the same features.
BIRD 9 (two images). Closer shots of a paler-headed bird clearly showing the rather masked appearance. The extent of the white tabs folding round onto the sides of the rump are more easily assessed here.
Following is another series of five quite distant birds, this time showing the upperside. The upperparts are generally quite brown, less dark than I'd expected, they only ever look blacker when flying directly away. The second bird has an abnormal white spot on the right wing.
Coming now to the first of two shearwaters I don't believe are Bannerman's. The first I suspect could be a Newell's, even if a couple of poor quality images aren't going to prove anything. I don't think anyone else on the ship noticed this bird, I was taking a break from my station at the rail and took a stroll around the top deck. On the sun-ward side of the ship I spotted this bird which immediately caught my attention as something strikingly different as it flew quickly past in the opposite direction to the ship.
The bird was smaller and far less rakish than the many Wedge-tailed Shearwaters P.pacificus but compared to Bannerman's it was longer- and slimmer-winged with deeper wing-beats and more purposeful flight. It wasn't possible to get a clear view of the undertail coverts other than to say they weren't extensively white as Manx Shearwater P.puffinus but generally plumage differed from Bannerman's in that it was darker above, less brown, when viewed side-on which created a stronger dorsal/ventral contrast more akin to Manx. Judging from on-line images this bird seems less black than might be expect of Newell's (which I've never seen) but I don't know how that taxon might look in different light conditions or how fading might affect its appearance.
The head and hind neck were uniformly dark, the latter lacked the obvious grey of Bannerman's, and the division between the fore and hind neck was sharp. Lacking a grey hind neck the upperparts were concolourous from crown to rump. Only the centre of the rump was blackish due to extremely large white patches wrapping round from the underparts. These were not only far larger than those of Bannerman's but more contrasting with the rest of the upperparts.
Unfortunately there was only time to grab a couple of shots before it disappeared. So strong was my gut feeling about this bird that it was only one of three birds that I felt compelled to check the images of in situ rather than waiting till dinner (my first close Bannerman's of course, and the possible Tropical being the others). The first image coming up is of a Bannerman's, at the same angle for comparison, then the bird in question.
BIRD 15 (one image). Bannerman's tended to look darker when flying directly away, this is a good example and the white tabs on the rump are obvious. The bird has quite chunky proportions.
Possible Newell's Shearwater. The white tabs on this bird are large, both in lateral length and reach across the rump, compared to the Bannerman's at a similar angle in the shot above. The wings are proportionately longer and slimmer than Bannerman's. It is also longer-tailed which can even be seen in this comparison despite the unfavourable angle. (These shots are slightly more heavily cropped than the others.)
Possible Newell's Shearwater. To my eye there's no doubt that this image shows a longer- and more pointed-winged shearwater with more of a Manx feel than any of the 'small shearwaters', this was definitely the impression I had in the field. Compared to Bannerman's at a similar angle, it's darker and more uniform throughout the upperparts.
Moving on to the second bird. This was seen by several people and was also of striking appearance in the field. At the time questions were being asked about it being a Newell's, though personally I didn't think so primarily because of the extensively dark undertail coverts (at the time I believed they were more Manx-like than they actually are) and the 'small shearwater' jizz. I put it down to an odd Bannerman's. With more time to check the images later I changed my mind as a number of features are at odds with Bannerman's but I still didn't think it were Newell's as it lacked large white rump patches and had the feel of a 'small shearwater'. Again I only got two shots of it and have posted two versions of each here, a second heavily cropped.
It was similar in size to Bannerman's though I can't say whether it might have been a little larger or smaller. As can be seen in these images it's a more delicate bird, longer-tailed and smaller-billed, though the specifics weren't obvious to me in the field. To be more precise the position of the wings is slightly different compared to the mid-ship wings of Bannerman's leaving a longer, more tapering rear. The bill is slightly shorter and slimmer, the tip in particular which looks a little heavy on Bannerman's.
The upperparts are uniformly dark brown, it totally lack's grey on the neck and thus shows a strong contrast between hind and fore neck. The underwing is slightly whiter due to less heavy markings along the leading edge of the hand and across the lesser coverts on the arm, the bases of the primaries are also greyer and paler. The undertail area is extensively dark but lacks the very sharp white and black divide of Bannerman's because a large extent of the vent is mottled dark which at a distance creates a greyish band between the dark undertail and white belly. Whether this is due to dark-tipped or dark-based feathers can't be made out in these images. On-line images of P.bailloni dichrous are the only ones I've found which share this feature.
Possible Tropical Shearwater. The differences mentioned above are all apparent in these shots plus there seems to be a pale eye-ring behind the eye in the very heavily cropped version. At this angle, and with the pale water behind, the bill looks rather small.
Possible Tropical Shearwater. I have no doubt that with these views the white spot in the centre of the tail shown by Bannerman's would be very obvious (perhaps the feet/toes are a different colour?). Again the bill looks very thin particularly at the tip. The dorsal/ventral contrast on the head and neck is much stronger than on Bannerman's while the underwing is lighter overall with less sharp contrast as is also true of the vent due to extensive mottling.
The dispersal of Newell's Shearwaters is little known and it's not such a stretch that they could reach these waters, especially non-breeding immatures. As 'small shearwaters' are less prone to long distance travel their appearance here might seem improbable though in a stong El Nino year it might be more likely that they could venture further north. It certainly seems that a number of species are being recorded north of their normal range in the east Pacific this summer.