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!
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.