[NatureNS] Tail length in Gyrfalcon and Peregrine

Date: Tue, 30 Sep 2008 12:28:19 -0300
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Hi All:

I thought I'd add my two cents worth, without judging sightings by others.

I have always found it odd that David Sibley should state Gyrfalcon is
"relatively long-tailed." This is true if one uses wing extension as a
criterion, as shown in his fine paintings of perched birds. But that is because
of relatively longer wings, not shorter tail, in the peregrine.

Overhead, Gyrfalcon does appear short-tailed and short-winged relative to young,
dark Peregrines. (That's another problem, because some of our eastern
peregrines are darker than they "should" be because of infusions of West Coast
stock during reintroductions.) The tail of Gyrfalcon does appear short, that
is, relative to the rest of the body and head. (You can actually get this from
Sibley's paintings by measuring tail lengths from undertail coverts on perched
birds or from back of wings on flying ones compared with length of the rest of
the body to tip of head.) And this is accentuated beyond the actual difference
in relative tail length because Gyrfalcons have notably broader closed tails
compared with Peregrines. So, altogether, they appear much chunkier than dark
young Pergrines. The set of photos URL'd by Blake Maybank immediately strikes
one as depicting a typical, long-tailed young Peregrine.

And, by the way, I too have sometimes made the mistake of confusing the two -
then later having second thoughts and scratching my record.

Cheers, Ian McLaren

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