Dead Bird (and other) Quiz Answers

21 04 2011

Only one taker on this quiz; Libby Rock sent this email:

“Here are some wild surmises for the EXCELLENT dead bird quiz this week.

Bird A:  Thomas says Great Blue Heron; I’ll go along with that.

Bird B: I say Cooper’s Hawk; Thomas says Harrier.

Other dead thing: I say Harbor Seal; T concurs.”

Not bad, Libby and Thomas. Bird A is a bit tricky. The shape of the beak and the sheer length of the neck (note the drinking-straw like trachea trailing off to the left) suggest a heron like bird. The reported culmen length of 97mm is rather large, but not quite into Great Blue Heron territory, which sport bills of 130-150mm. While it is somewhat difficult to accurately measure culmen in a mummified skull-head like this, 40mm would be quite a large way off. What of other herons then? Black-crowned Night Herons have culmen lengths between 73 and 84mm (a bit small) and Great Egrets lie between 104-116mm (still a bit large). Outside of herons, what other possibilities are there? We must entertain the loons with a chisel-like bill like this, and their culmen lengths are closer: 74-91mm. But take a look at these photos:

Common Loon: The bill looks about equal to, if not slightly shorter than, the head.

Great Blue Heron: Bill is substantially longer than the head itself.

The loon’s head is a good deal blockier than the heron’s, and the bill appears deeper than the more spear-like heron bill. So certainly, we appear to be dealing with a heron species in our Bird A. Based on the culmen length, and without any plumage to examine, Great Egret appears closest to the mark, so let us go with that.

As for Bird B, Cooper’s Hawk was one of my initial guesses as well, based on the barred tail. But on closer inspection, particularly of the feet, it appears that this bird is a member of the buteo group, rather than the accipiter group. Buteos, such as Red-tailed Hawks and Red-shouldered hawks, are generally heavier bodied, with much more robust feet. Accipiters, like Cooper’s Hawks and Sharp-shinned Hawks, are overall slimmer, and their toes and talons are particularly long and slender. Accipiters tend to prey on birds, while buteos tend more toward rodentine prey. Bird B looks to me most like a juvenile Red-tailed Hawk. When young, this species lacks the eponymous rusty red tail, and instead sports a brown, barred tail.

A living juvenile Red-Tailed Hawk. Note the barred tail.

Buteo foot versus accipiter foot. Bird B appears more the former.

Finally, other dead thing. Yes, a seal. Beyond that, I profess no particular knowledge. Barbara Grunden, who found the specimen, tells me that a professional from the marine mammal stranding outfit up there in Maine told her it was a Grey Seal pup. All I know about seals can be summed up thusly: Harbor Seals are very cute. Grey Seals are kind of creepy looking. Now THAT is scientific. So I will defer to the pro and say Grey Seal pup.



One response

21 04 2011
Mary Wright

Sorry I missed the latest quiz. Don’t know your source for measurements, but you might like to know that Peter Pyle’s Identification Guide to North American Birds, Part II, puts exposed culmen length of Great Egret at 98-124 mm. The 97 mm measurement might cling to the very bottom end of that range. The only other heron that “fills the bill” (ahem!) would be Tricolored Heron at 88-108 mm. The Tricolored is found in Florida, but I think the bill is more slender and proportionately longer . . . so I’d agree with the Great Egret choice. Not so happy with the Red-tailed Hawk; wish you had more measurements.

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