Back to business! (Dead Bird Quiz answers)

19 07 2011

Your SEANET blogger is off to meet Dr. Julie Ellis’ baby today, but first, I cannot shirk my duty to the DBQ. I was shocked, shocked! to discover that no one had proffered any answers whatsoever on this quiz. Is anyone even out there?!

Well, despite the lack of response, I shall fling my thoughts on these carcasses into the void.

Juvenile Iceland Gull: our Bird A?

Bird A is a true stumper. As I see it, there are a few options: Glaucous Gull, Iceland Gull, and some sort of albino/leucistic Herring Gull. Glaucous Gulls are bigger on every score than our Bird A, and aside from that, the youngsters of that species tend to have a brownish coloration on a generally white base, not nearly so white overall as our specimen. In terms of size, this could be either a Herring Gull or a Iceland Gull. So, how can we make this determination? Well, the bill is on the large side of the range for Iceland Gull, and seems a bit heavier/stockier than a Iceland Gull’s. Still, that is rather subjective. Juvenile Herring Gulls and Iceland Gulls both have a generally pink bill with a black tip, so that doesn’t help much.

Our Bird A appears to have white legs. While beached carcasses can bleach out in the sun, we don’t usually see complete bleaching of all pigment, so that feature tends to push me toward the idea that this is a leucistic or albino Herring Gull. Albinism results when the pigment melanin is not produced. In complete albinos, this means even the eyes and skin lack any melanin, and generally look pink where the blood vessels show through the unpigmented tissue. Colors not produced by melanin (many yellow pigments, for instance) can still occur in an albino. Leucism, on the other hand, is a failure of pigment to migrate to places where it normally occurs. This applies to melanin as well as other pigments, so leucistic birds may lack all pigment in part or all of the body. If we take the white color of Bird A’s legs as a real phenomenon, and we know that the legs in both Herring Gulls and Iceland Gulls are normally pink, then that would tend to indicate a leucistic bird who retained pigment in the bill. It’s impossible to know what color the eyes are since they are closed in the mask of death. Also not helping matters is the advanced state of dishevelment in this bird. Iceland Gulls and Herring Gulls are often differentiated by “expression,” an amorphous assessment of head shape, bill proportions and the general attitude of the bird. This one is dead and missing most of its head feathers, so it’s hard to say whether it would have resembled the rounded, innocent looking head of an Iceland, or the scheming, fierce head of a Herring Gull.

The final, confounding factor is that, while some signs point to leucistic Herring Gull, such birds usually retain some paler “ghost” version of their normal plumage. So, while the overall color of the leucistic Herring Gull pictured here is whitish, there is still a substantial brown color to the primaries (which would normally be dark brown or black). Our Bird A doesn’t seem to have any of that retained brown pigment in what’s left of the primaries.

So, sigh. I fear this has been nothing more than a diverting argument with myself. I need to move on to Bird B.

Bird B has lobed toes! Or did, once upon a time, and still has some shreds of them left. So, that means Bird B is a grebe. Not much to this bird beyond a puff of feathers, so going simply by the tarsus length, which is small for a grebe, my best guess is that this is a Pied-billed Grebe. On this one, bird expert Dick Veit agrees with me, which is a relief and is how I will end this fruitless discourse.

Leucistic Herring Gull: is that you, Bird A?



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