Dead Bird Quiz answers, at long last

18 06 2013

An inexcusable delay in posting these answers–I blame my travel debacle of late last week. More on that next time. As for the DBQ, I must thank the universe for bringing Wouter to this blog as Bird A is a perfect example of how dead bird i.d. is basically nothing like live bird i.d. Wouter posted this explication on Bird A:

Bird A has a very wide pelvis, a shape that is typical for a goose or duck. The wing is white with black primaries, which fits snow goose or male eider. Because there may be a black secondary and a few black body feathers in the picture, my guess is male Common Eider (Somateria mollissima)

Interestingly/coincidentally, we did have our very first snow goose reported to the database back in April. Wendy Stanton found this bird on Pea Island in North Carolina:

What do you think of that!?

What do you think of that!?

We don’t even have snow goose as an option in our species list! In all honesty, I wouldn’t know a snow goose if it hit me in the head, but after seeing Wendy’s report, it looks like a good fit. Anyway, if you look at this photo, you’ll see the darker primaries that Wouter mentioned. But male eiders have those too, and when in doubt, it’s generally best to go with the common species. As we learned in vet school, when you hear hoofbeats, think horses, not zebras. Of course, being a wildlife vet, this is probably less reliable advice for me…

Bird B is far more intact than Bird A, but still poses some challenges. The feet are useful, and in the photo, it’s clear that all four toes are webbed, marking the bird as a pouchbill (cormorants, pelicans and such.) Though the bill is not fully visible here, we can say it’s no pelican. The wedge-shaped tail says cormorant. But which kind? We don’t have measurements on this bird, and devoted blog reader BiologistOnTheEdge (not her real name) points out that in field guides for normal people (i.e. live bird field guides), cormorants have reported body lengths of over 90cm, and this bird looks smaller than that. It’s a point that got me thinking–what is the deal with those body lengths given in live bird guides? How can you even judge that in a live bird? And is it the measurement from bill to tail tip? Or to toetips? In any case, it’s true that this bird is not 90cm long. But it is a cormorant nonetheless.
The amount of white on the belly tells us this is a juvenile, but of which species? The head is so weather-beaten we can’t really see the throat color, which would have a white patch in a great cormorant and would be brown in a young double-crested. The belly of this bird is quite white looking, so I was initially thinking it was a young great cormorant, whose bellies look like this:

A juvenile Great Cormorant. (photo by Libby Rock)

A juvenile Great Cormorant. (photo by Libby Rock)

Lots of white on the belly, contrasting with a brownish neck. Double-crested cormorant juveniles, on the other hand, tend to have a more brownish overall color to the neck and belly, with little contrast between them, like this:

Juvenile DCCO (photo by S. Courchesne)

Juvenile DCCO (photo by S. Courchesne)

The difference seems quite obvious until you consider that juvenile DCCOs can also look like this:

Juvenile DCCO (photo by Gil Grant)

Juvenile DCCO (photo by Gil Grant)

or even this:

Another one (photo by E. Walker)

Another one (photo by E. Walker)

What Sibley notes as “variation in color of juveniles” is, therefore, quite substantial, and to my mind would include the amount of paleness in our Bird B, especially noting the lack of contrast between breast and belly. And though I don’t take much stock in wing chords guesstimated from photos, this one does seem small enough to be a double-crested.

As usual, I am open to arguing this one back and forth, so if you think I’m missing something, please, dear readers, do call me out. I know you’re not shy about that anyway.

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2 responses

19 06 2013
Wouter van Gestel

You may be right about DC cormorant. I forgot to take into account that at your side of the Atlantic you have a different subspecies of greater cormorant. This bird fits a Phalacrocorax carbo sinensis, which we have in Holland, rather well, especially a female. However, it is too small in overall size and bill for a P. c. carbo, which lives in the US.

By the way, no need to thank the universe, thank Google 😉

19 06 2013
Biologist on the Edge

Once again I am wrong. Hmmm. Maybe I should quit doubting Wouter and try to learn from him instead.

When is that dead bird field guide coming out? Clearly my experience with live birds is not as helpful in identifying the dead ones as one would expect.

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