Geography Reference
In-Depth Information
The dark-eyed junco I held lived more than a century ago in the forests of
Labrador. The small, black-and-white “snowbird,” as the species is often called,
was shot in 1891 for science. Its collector, likely L. M. Turner from the Smith-
sonian Institution, expertly skinned and stuf ed the sparrow-sized animal,
preserving its outward anatomy—part of what an evolutionary scientist would
call the “phenotype”—for future biologists such as myself to inspect. I care-
fully spread its tail, which consists of twelve feathers, six on the left mirroring
six on the right of the bird's midline.
The junco's snowy outer tail feathers contrast strongly with the charcoal
inner ones. As juncos l it between bushes, this white l ag is conspicuous, but
it is quickly furled out of sight when they land. The sudden disappearing act
may confuse a predator in pursuit, while during l ight the white signal may
serve to organize the escaping l ock. Both sexes have white edges to their
tails, but males have the most, and they l ash this signal to would-be rivals as
they defend breeding and feeding sites. Aggressive males chase one another
among the bushes and through the airspace with their small tails spread out,
revealing the white, like poker players laying fans of cards on the table to com-
pare their hands. The junco with the most white wins. The old guy from Lab-
rador was a winner. Each side of his tail held two fully white outer tail feathers
and a third that was nearly all white. I scored him a 5.6, meaning that 5.6 of
his 12 feathers were white. I've seen only two males with whiter tails.
The bird collection at the University of Washington's Burke Museum has
a lot of juncos. Thankful for the large number of specimens, I used them to
peer back in history and see how junco tails have changed. Several hundred
were arranged before me, belly up and toe-tagged, liked stif s in a morgue. I
reasoned that the male aggression that accompanies a big white tail probably
earned my Labrador junco a place here as he pushed a bit too close to the gun
