Monday, September 21, 2009

Quiz #318 (2009-3-13) Answer

Click the picture for a larger view.

Answer by Tony Leukering

We had a doozy for the final quiz of the quarter, and I took the picture at Cape May Point SP, Cape May Co., NJ, specifically for this quiz. As has happened a couple of times previously, the quiz turned out to be more difficult than I had intended; there was an intended hidden bird, but also an unintended one, with the latter being quite difficult, if even truly possible. But, we'll start with the easy beasts, ignoring the partial (and unidentifiable) birds on the extreme left and right edges of the frame, and work from left to right.

The leftmost whole bird is on the back of the structure facing left and has the classic strongly bicolored orange-and-black bill of breeding-condition Forster's Tern. The next bird to the right has somewhat redder legs and a bill that is both redder and with the black not sharply set off from the red. The legs are not particularly short, so this bird is an alternate-plumaged Common Tern in breeding condition. The next smaller tern to the right is another Forster's (again, orange legs and orange-based bicolored and thicker-based bill) with another Forster's well in the back behind the huge tern. That huge tern has a crown that is mostly white, black legs, and a stout bright orange bill. The size rules out Elegant Tern, which would not so greatly dwarf Forster's Tern and the bill color and head pattern rule out Caspian.

The next tern to the right looks quite different from all the others, but it has the distinctive and classic robbers's-mask appearance of basic-plumaged Forster's Tern, and that's what it is. the bird perched on the pole is also a Forster's, as is the smaller tern to the right of the basic-plumaged Forster's. The next bird to the right (in the back) is unidentifiable, so we'll continue on to the next huge tern. Like the Royal to the left, this bird has black legs and a large orange bill, but it sports a solidly black crown. The bill seems a bit smaller than that of the Royal behind it, but it's still too deep-based to be that of an Elegant Tern and the bird's size also rules out that species, leaving us with no options other than an alternate-plumaged Royal Tern. The next two identifiable birds, the one between us and the second Royal and the one lying down are both Forster's by bill color and size.

Now, we come to the tricky bits, as the next five birds have some important bits hidden. The left-most of these in the front rank seems to sport redder legs and bill, but it also shows the distinct demarcation of black and orange on the bill typical of Forster's Tern and quite different from our other medium-sized terns. Perhaps, the apparent redness is an artefact of the different angle at which the bird is perched. Regardless, if it isn't a Forster's, it would have to be a Common, so it really doesn't matter what we call this bird -- for the quiz, anyway.

The next two terns have black legs and one is perched facing us but with its head turned back preening under its left wing. It's obviously a large tern, but the view we have probably does not permit definitive ID, but I can tell you that there were three Royal Terns perched here when I took the picture and this one is the third one. Its black-legged neighbor, however, was the intended hidden bird and the majority of incorrect respondents missed this one. In addition to its black legs, it has a mostly black bill with a distinct yellow tip that is angled down and backward as the bird seems to be studying its toes. This feature, in combination with its size being intermediate between that of Royal and Forster's clinch the ID as Sandwich Tern.

Skipping ahead to the rightmost whole bird, the bright orange legs suggest that it is another Forster's Tern, but it may not be strictly identifiable. The last two birds are both banded, though the legs of these birds are somewhat Escher-like in that it's puzzling as it is not easy to determine which legs belong to each of the birds. I believe that the right two legs (the left of which is banded) belong to the front bird and the left two legs (the right of which is banded) belong to the back bird. I base this mostly on the fact that the left two legs look thinner and redder than do the others. The seeming thickness difference could, I admit, be an illusion. The bird in front has a very long tail and we can see the inside edge of the left fork of that tail. It seems to me to have the somewhat darker inner-edge tips typical of Forster's Tern and so different from the tails of Common and Arctic terns, which have dark outer edges to the tail. However, I'm not positive that I'm interpreting the tail correctly and one respondent suggested that the bird is a Roseate Tern. Regardless, I'm not convinced that the bird is definitively identifiable.

That leaves us with the single bird present whose entire body is within the frame, but of which bird we can see the least. If it weren't banded and didn't have such an odd bill coloration, we might be able to ignore it as unidentifiable, but it is banded and it does have a barely-red-based black bill. The bill, alone, suggests Roseate Tern, but that in combination with the band make the ID nearly definitive. (Virtually all of the Roseate Terns that show up in Cape May are banded, as all of the colonies of the species to the north of New Jersey are extensively studied and banded. Unfortunately, in the field, I decided after quite some time studying this bird, that it was not a Roseate Tern and that the bird in front of it was a Forster's Tern. Upon running the quiz, though, I had second thoughts and asked Michael O'Brien for his opinion of the black-billed bird. He responded:

"Wow, that's a tough one. The bill looks long and the appropriate color for Roseate, and the sliver of white below the cap looks thinner than that on the Common Tern in the left side of the photo. I can't tell whose legs are whose, but one of the banded legs looks nice and coral red, while the other looks more orange like a Forster's. Same bird? I wish I could see ANYTHING else to back it up, but I would say it's probably a Roseate."

Of course, if I cannot be sure of the ID of a bird in one of these pictures, it is not fair to expect respondents to get such individuals correct, so I did not count those responses lacking Roseate Tern as incorrect if all else was correct. However, I did give the three respondents proposing Roseate Tern as one of the species present an extra bonus point each.

Twelve respondents provided answers with no incorrect species, but without enough correct ones.

With this being the last quiz of the quarter, it is time to announce the quarterly winner. Mark Dettling, Al Guarente, and Peter Wilkinson all ended the competition with 11 correct and congratulations are due all of them. As Peter has already won a quarterly competition this year, he is ineligible for another. Thus, the single bonus-point total difference between Mark and Al (9-8) leaves the former the winner of the third quarter's competition. Honorable mention goes to the next three places, occupied by Robert McNab (10 correct), Aaron Brees (9), and Margie Joy (8). As far as the annual competition is concerned, Aaron Brees still holds a three-quiz lead coming into the final quarter.

Incorrect species provided as answers:
Elegant Tern - 1
Large-billed Tern - 1
Caspian Tern - 3

The 6 of 24 providing the correct answer:
Tyler Bell
Nick Komar
Mark Dettling
Kevin Kerr
Peter Wilkinson
Bryan Guarente

Answer: Common Tern, Forster's Tern, Royal Tern, Sandwich Tern (and, perhaps, Roseate Tern)