Monday, December 21, 2009

Quiz #329 (2009-4-11) Answer

Click the picture for a larger view.

Answer by Kevin Kerr and Tony Leukering

The last quiz of the quarter and the year and what an odd one! I liked a part of Aaron Brees' response, so have provided it below.

"This is a weird picture if you don't know what is coming.

1. gannet with fish
2. enlarged the photo; gannet with small black and white bird (alcid?) in its bill
3. no, that is a loon did a gannet get hold of a decapitated loon head?
4. oh...the loon is swimming behind the gannet in a wave trough that hides most of the bird
5. reaction #3 was pretty stupid."

Kevin Kerr provided a more thorough analysis, so we'll continue with his thoughts.

"Let's start with the more obvious bird in this picture. It is nicely posed, unobstructed, and can be quickly identified as a sulid. The mostly white body, tidy black mask, blue eye, and subtly yellow-tinged head are perfect for Northern Gannet (no other gannets occur in the ABA area, though the limited distribution of black on the wings should eliminate them, anyway).

"So now on to the more challenging question: what bird is that gannet eating? Or, whose head has been digitally superimposed on this image? Okay, there isn't much showing, but it's apparent that we're looking at just the head of a diving bird poking out of the water. The shape of it (elongated, with an angled crown that appears to sag just a little in the centre [ah, those Brit-types never could spell; I mean, what's with all those extra 'u's in words like 'color?']) reveals that it is a loon and the colour pattern indicates that we are looking at either a juvenile or a winter-plumaged adult. The darkness of the head eliminates Red-throated and Yellow-billed, but the remaining suspects still present an awful challenge.

"Arctic Loon is incredibly difficult to distinguish from Pacific, but the odds of seeing one next to a gannet are so astronomical that I'm comfortable removing this suspect for now. This leaves Common and Pacific, which can still be surprisingly difficult to separate. Common is much more likely (given the company of a gannet), so it wouldbe logical to use that as our null hypothesis and see if there is enough evidence to change our minds.

We cannot see the neck pattern, which is quite unfortunate as that would help a lot! The head shape does not look quite as rounded as I would expect for a Pacific Loon (recall the sagging centre mentioned above). The dark cap does draw to mind Pacific (contrasting highly with the white underparts and appearing not to extend below the eye), but closer inspection reveals a lighter area above the eye and a general patchiness to the dark areas (more consistent with Common). I would also expect white ear coverts if it were a Pacific, whereas our bird is dark here, too. Lastly, the gannet, which is in the foreground, is a big bird. Pacific is at best a medium-sized loon and, although only the head is showing, I suspect that a Pacific would look dwarfed beside this larger seabird. Given the available evidence, I will have to settle on Common Loon."

Thanks, Kevin. However, I disagree with one of his theses: that it would be odd to see an Arctic Loon next to a Northern Gannet. It certainly might be in the New World, but the two are broadly sympatric in the eastern North Atlantic. It would actually be much rarer to find Pacific Loon and Northern Gannet together and it may be more reasonable to throw out Pacific on that basis. Regardless, I believe that both Arctic [note: TWO 'c's] and Pacific loons are eliminated on the head/neck pattern and coloration. Our bird shows an extension of dark coloration from the auriculars down to the edge of the throat. Both of the medium-sized loons should show pale auriculars. Though Pacific Loon does usually sport a chin strap, the connection to the dark of the head is nowhere near as extensive as might be suggested by our bird's dark protrusion toward the throat. Additionally, the head's blockiness would probably be extreme for Pacific Loon, though within the range of that of Arctic Loon.

I photographed this Adult Northern Gannet and basic-plumaged Common Loon off New Jersey on 9 November 2009. The loon is actually on the water's surface; its body is mostly hidden by a 1' swell on a very-light-wind day.

Three respondents got no species incorrect, just didn't provide enough correct ones. additionally, one respondent's answer was precluded from being correct for the competition as it lacked one of the 'n's in 'gannet.' Another's, that would have been correct had the loon been of a different species, would have been precluded from being correct for the competition as it lacked one of the two 'c's in 'arctic.'

Only rarely does anyone get a perfect score in a quarterly competition on the Mr. Bill Mystery Quiz, so it's particularly spectacular that THREE respondents did it this quarter. Thus, I extend hearty congratulations to Kevin Kerr and the Such brothers, Marcel and Joel for accomplishing the feat! Unfortunately, that means that I have to toss a three-sided coin to come up with the actual quarterly champ. As the random pick among the three landed on one of the Such brothers and because I'd like to not be an instigator of family strife, I've decided that Marcel and Joel will share the prize of a year's membership in the Colorado Field Ornithologists.

As for the annual competition, Aaron Brees took sole possession of first place in the second quarter and refused to let go, getting 37 of 50 correct. Four respondents, Mark Dettling; Al Guarente; Robert McNab; and Peter Wilkinson, each got 32 correct. Congratulations to Aaron for winning the annual-competition prize of a registration fee for a Colorado Field Ornithologists' convention.

Incorrect species provided as answers:
Pacific Loon - 7
American White Pelican - 1
Arctic Loon - 1

The 16 of 28 providing the correct answer:
Al Guarente
Robert McNab
Kirk Huffstater
Aaron Brees
Tyler Bell
Kevin Kerr
Chris Warren
Su Snyder
Jim Beatty
Jen Vieth
Nick Komar
Barbara Deneen
Nancy Hatch
Peter Wilkinson
Joel Such
Marcel Such

Answer: Northern Gannet, Common Loon