Dead Bird Quiz becomes tournament of champions

13 02 2013
Our Bird A once looked more like this masked bandit.

Our Bird A once looked more like this masked bandit.

I’m glad I postponed this DBQ answer reveal, because we ended up with a wealth of responses. First to ring in was James Taft, suggesting Forster’s Tern for Bird A. Subsequent guessers Mary Wright and Wouter van Gestel concur, as do I. It’s a relatively easy thing to identify an intact carcass. For the dead bird enthusiast looking for pointers on this i.d., the Forster’s Tern (FOTE) is most likely to be confused with the Common Tern (COTE). Notable differences: in non-breeding plumage, FOTE have a dark “mask” encircling each eye with a lighter nape of the neck. The COTE, on the other hand, always has a black nape, and either a complete or partial black cap, depending on the season. Breeding FOTE also have a black cap, however, so in that case, the bill color can be of help. It’s dark orange-red in breeding COTE, and pale orange with a distinct black tip in breeding FOTE.

Bonus on our Bird A: it’s a species for which we needed pictures for the upcoming Field Guide, so I was doubly excited to see this one submitted to the database!

Is that you, Bird B? (Sooty Shearwater in flight)

Is that you, Bird B? (Sooty Shearwater in flight)

Bird B generated a collection of conflicting identifications from four contestants: Juvenile Laughing Gull (James)? Black Gull (Nancy)? Sooty Shearwater (Mary)? Greater Shearwater (Wouter)? This always unnerves me since I do not claim to be an expert at making these identifications and I always feel best when I get a roaring consensus. In this case, I did get a welcome opportunity however: a chance to try out the Wing Key I’m developing for the Field Guide. Following my own key lead me thusly: dark and unmarked upperwing? yes. underwing light? yes. Wing chord greater than or less than 15cm? (and I am aware I failed to give you this info, dear readers; it was 27cm) yes. Underwing light but with darker leading edge? yes.

So here’s where it got tricky. The next question in my key is “clean white central underwing? or “smudgy white underwing”? In our Bird B, the light underwing doesn’t look entirely clean white, which would lead us to an i.d. of Greater Shearwater. But it doesn’t look quite as smudgy gray as your typical Sooty Shearwater (the other likely option) either. Based on the wing chord of 27cm, I’d lean toward Sooty though.

Wouter’s point that the underwing just doesn’t look dark enough to be a Sooty is well taken however, and leaves me whipsawed with confusion. In this case, it may be the safest bet to call this one “unknown shearwater.” But if I’m bold, I may commit to Sooty. But I’ll choose “somewhat confident” on the dropdown menu if I do, you can be sure.

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2 responses

14 02 2013
Wouter van Gestel

This is a tricky wing indeed. I just remembered I had a dead sooty shearwater in my freezer, and I have it on my desk right now. Unfortunately, the mystery wing does not fit this species. Sooty does have some whitish feathers on the underside, but less than in this wing, and those feathers have dark shafts in sooty, not white like in this wing. Furthermore, this wing has in the armpit some white feathers with a dark centre, and in sooty shearwater, the feathers in that part of the wing are all dark. Also, the dimensions of this wing are different than my shearwater, this wing is wider and has a shorter hand. So it may not be a shearwater at all (If I could add pictures to this message I would show you). I cannot make a direct comparision with greater shearwater (extremely rare in Holland) but I asked a friend who may have a wing of this species in his freezer. Anyway, I’m a bit at a loss with this wing, I may have to call in an expert on this one.

15 02 2013
sjcourchesne

I had the same reservations about the wing shape, though it’s also hard to be completely certain about that since the proximal feathers are all missing. I do agree that there is too much nice clean white to make this an easy i.d. as a Sooty. I keep thinking this might be a species I haven’t even considered yet. That has happened when a wing actually came from a non-seabird, since those are not really on my radar. Let us know what you conclude, Wouter; I’m leaving this i.d. open for a while longer since it makes me uneasy!

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