Monday, May 18, 2009

Quiz #300 (2009-2-08) Answer

Click the picture for a larger view.

Answer by Tony Leukering

In honor of this being the 300th Mr. Bill Mystery Quiz photo, I wanted to present a challenge to our players. Well, more of a challenge than is typical. I thought that if I presented a picture with at least one obvious bird of uncertain ID, then some viewers might think that that was the hidden bird in the picture (something that regular players know is a regular feature of this quiz). This might cause some misdirection and keep folks from searching for the truly hidden bird.

One might take umbrage with an obvious attempt to trick our players, but the primary reason that I spend so much time at the task of being Mr. Bill is that it offers me a chance to instruct, something that I find most enjoyable. One of the topics that I tend to focus on, in this and more personal venues, is to identify every bird in front of you, taking nothing for granted -- a thing that I learned from watching David Sibley. So, this picture provides yet another example of a crowded picture that really requires a bit of effort in order to come up with the correct answer. And, that expenditure of effort is all I ask.

Let's start with the easier birds. In the front right, there is a straightforward adult Ring-billed Gull, with its yellow bill with distinct black ring. Note that the head has little of the typical basic-plumage streaking, suggesting that the picture was probably taken after February and before October. There is another Ringer in the picture, the bird in the back right that undoubtedly was mistaken for a Mew Gull. However, the bird has distinct black bands on both maxilla and mandible and the darkest part of the bird's head streaking is NOT on the nape, as it is in Mew Gull. The mantle does look darker than the bird behind it, but that bird is not only a different species but is in a plane different from that of the Ring-billed Gull -- the back bird is more nearly perpendicular to our view than is the Ringer, whose back end points somewhat away from us.

As all respondents noted, there are also terns present. In fact, there are five present in the picture, all but one being in the middle, from back to front. The bird most easily IDed is the front-and-center bird facing left that has the distinct eye patch typical of Forster's Tern (see below on the name of that species). This bird's crown is not white; it appears gray in contrast to the black mask. That appearance is due to the bird's pre-alternate molt and the resultant incoming black feathers. That places the picture as being taken after February. This appearance might also rule out a fall date. The tern in the middle center is also, obviously, a Forster's Tern. The tern in the left back is also such -- the mask is obvious. The final two terns are a bit more tricky and, hopefully, were the cause of most (if not all) the answers with incorrect tern species listed. The left of the two terns in the back center has the appearance of a mask but the angle of the head makes it seem as if the black continues onto the nape. However, we cannot be sure of this fact and need to look elsewhere for confirmation or refutation. Before we go on, note that the two Forster's Tern in front of this bird have very pale primaries, thus we can be certain that the picture was not taken in late summer or early fall when the species would have darker primaries (from having the whitish bloom wear off revealing the true darker color of these feathers).

The left of the two back terns seems to have a bigger, darker bill than the two in front of it, but the picture's plane of focus does not allow certainty in this regard. However, the bird's legs seem fairly long for a tern and similar in length to the definite Forster's Terns present. Despite the bill's seeming thickness, the ratio with its length is still that of a Forster's Tern and not that of a Gull-billed Tern. The right of the two terns is the most problematic and, undoubtedly, accounts for the various answers of Common and Arctic terns, due to the apparently shorter legs. Note, though, that the substrate has numerous dimples and that the bird is standing in one -- we cannot see its toes. Thus, the apparent leg length could be misleading. The primaries on the bird also appear quite pale, so the bird is not a Common Tern. It also appears to have actual black on the crown, unlike any of the Forster's Terns present. However, as both of the more-forward two Forster's have incoming black in the crown, there's no reason to suspect that this bird might not be a Forster's further along in the pre-alternate molt than are the others. Though the bird seems unidentifiable to this point, the apparent whiteness of the underparts would rule out Arctic Tern, but not Roseate. So, though I know that the bird is a Forster's Tern, I am not certain that we can specifically identify the bird given this one view.

We are now left with the remainder of the gulls. Many are readily identified as Bonaparte's Gulls in basic plumage, thus the photo was taken before May and after September (or so). They are IDed by their pale pink legs; thin, black bills; dark ear spots; and wingtip pattern. The bird lying down behind (in both respects) the front Ring-billed Gull, shows that wingtip pattern of white outer primaries with wide, dark tips to best advantage. The preening individual near the left end seems to have more black in the head than do others and has probably initiated its pre-alternate molt. So, all these smaller gulls are either readily IDed as Bonaparte's Gulls or are, possibly, unidentfiable given the single view that we have.

All, that is, but one. As at least one respondent noted, the actual focus of the quiz photo is the gull preening its back in the middle center. With care, one might have first noted it by one of a couple of features: its much redder legs or its paler mantle, compared to the Bonaparte's Gull between it and us. Upon closer -- and enlarged -- scrutiny, we might also note the different wingtip pattern of the bird. On that bird's right wing, the view we have of which is of the underside, there is much more black present than can be accounted for in the wingtip of an adult Bonaparte's Gull. And, as we've already noted the brighter legs that would rule out an immature Bonie, we can also see that the bird does not have any suggestion of black in the tail that should be present in an immature Bonaparte's Gull. These features all point to an adult Black-headed Gull. I provide, below, three other versions of the quiz photo with labeling (F = Forster's Tern, R = Ring-billed Gull, BH = Black-headed Gull; all others are Bonaparte's Gulls), the last two of which are subsequently more-enlarged sections of the quiz photo. The final picture points out each of the two wingtips of the Black-headed and the Bonaparte's in front of it and the dark patch in the primaries of the Black-headed.

Click the pictures for larger views.

I took this picture on the Delaware Bayshore of Villas, Cape May Co., NJ, on 29 March 2009. Note that the plumage state of the various species and their mere presence ought to be sufficient to rule out Arctic Tern, a species that really ought to be in the Southern Ocean -- or, at least, not somewhere where there is a bunch of northern-hemisphere larids conducting their pre-alternate molts -- at the time of the picture's exposure.

I would like to take this opportunity to send a big "Kudos" to Bill Maynard, the original Mr. Bill. Well, the original one after the clay version. (Too young to understand that last? Google it.) He devised the quiz and ran the first 100 (or so) of the quizzes. Obviously, his idea has been populat. Also, I'd like to send out my heartfelt thanks to all those, in the past, present, and future, that played our game. Without them, I would have no reason to do this job. I also want to expressly congratulate those few getting this anniversary edition of the Mr. Bill Mystery Quiz correct -- your effort at getting it right makes my effort at presenting these quizzes even more worth it!

Eight respondents provided answers with no incorrect species but without enough correct ones, all missing the Black-headed Gull.

One of the incorrect respondents that provided one too many species submitted an answer that would have been precluded from being correct for the competition as "Forster's Tern" was misspelled in it. I have no idea why, but a fairly large minority of birders think that the bird was named after someone that managed trees and insert that extra vowel -- thus an extra syllable -- into the name, creating "Forester's Tern." Having once known a birder with the last name of 'Forster' and having had many people butcher my own name (even though if one knows anything about Germanic languages, it's easy to pronounce), I can be fairly certain that Dick Forster may have been just a wee bit peeved at times when he heard folks mispronounce that tern's name. Perhaps others should think about their own names in that vein.

Tallies of incorrect species provided in answers:
Gull-billed Tern - 1
Common Tern - 4
Arctic Tern - 2
Mew Gull - 1
Ross's Gull - 1
White-winged Tern - 1
Roseate Tern - 1

The 7 of 23 providing the correct answer:
Mark Dettling
Tyler Bell
Su Snyder
Aaron Brees
Peter Burke
Bryan Guarente
Andrea Smith-Guarente

Answer: Bonaparte's Gull, Black-headed Gull, Ring-billed Gull, and Forster's Tern