First off, the easy one. All respondents (and there were many this time, thanks!) pegged this one as a Sooty Shearwater. For the i.d., I registered two things–clearly a tubenose beak, and the underparts (belly and breast) are all gray. This latter characteristic sets it apart from the other shearwaters, as they have either entirely white underparts, or mostly white (Greater Shearwaters have variable smudging on the belly). The mini tubenoses, like storm petrels, may also have dark underparts, but those guys are tiny and not like our Bird B.
Bird A didn’t seem to stump many people either, despite the lack of a head. For me, what I looked at first was the broad body, looking almost wider at the back end than through the breast; legs set far back on the body; and short, but broad wings. These things together say “diving duck” to me, and the options are typically scoters or eiders (and they’re pretty uncommon so far south). Mergansers would usually have a slimmer body overall, and the feet look too dark for them anyway. So, scoters. White-winged can be ruled out since our Bird A lacks the eponymous speculum. That leaves us with Surf Scoter and Black Scoter. This is a call I have to make often, and it’s not always easy when the head is missing. Wing chord is not a lot of help, since both fall in the 20-25cm range. There is a little trick that is sometimes useful when the outermost primaries can be seen clearly: in Black Scoters, the outermost primary is shorter and narrower than the next two, while in Surf Scoters, it’s longer. This can be subtle though, and when one is working from a photo, it may not be a helpful point at all. I do find the feet to be sometimes helpful, and Black Scoters have darker feet than Surf Scoters, even when young. Male Surf Scoters tend to acquire their reddish feet rather early, in my experience, and Bird B’s feet, by contrast, are very dark.
Mary Wright cited one of my favorite sources for making these calls: Peter Pyle’s Identification Guide to North American Birds, Vol. II. Mary pulled out these characteristics as being decisive in this case:
“Bird A: Black Scoter, second-year male. Species indicated by shape, size, and primaries that are paler on the underside. SECOND-YEAR because: dark upperparts and breast “contrasting distinctly with pale brownish abdomen, the latter wearing to whitish by May-Sept” (Peter Pyle, Identification Guide to North American Birds, Part II, pp 138-139); older birds have dark brown abdomen. Second-year MALE because: “upperparts and breast brown, increasingly mixed with blackish feathering … in Dec-Sept” (ibid); in SY females, brown upperparts and breast are “increasingly mixed with darker brown feathers in Nov-May” (ibid).”
Wouter wrote that it appeared to be a very faded female Black Scoter to him, and that raises a good point. That very pale brown color to the wings and back–is that real, or an artifact of time and weathering? Indeed, looking at the feet, they are contracted and dried out, almost mummified, indicating that this bird has been dead a good long time. We do see plumage bleach with time, so identifications must be made with a nod toward that phenomenon. But what IS clear from these photos is that the feathers replacing the old brown ones are coming in black (this is best seen over the back). That, as Mary points out, makes this a male, as in a female, those new feathers would be growing in brown instead.
This has been a good one for me to puzzle through, pondering each characteristic in turn. It’s impressive how far along one can get with a headless bird, no?
And now, I must go back to trying to finesse my pack for an end-of-school backpacking adventure with my sons. And they can’t carry much, so smart packing is going to be key here.
I leave you with something else Mary Wright shared with me, and which I, in turn, am sure you’ll want a look at. Some strange nest fellows these…