The owls we catch are largely
migrants, but the growing interest in saw-whets has also given
us a much better sense of their
breeding distribution outside the
boreal forest, which, like their
range in migration, is far wider
than we suspected. A survey of
random forested area in Pennsylvania found them on nearly
half the routes two years in a row
(though with little overlap from
one year to the next—perhaps
that nomadic nature once again).
They’ve been found nesting in
isolated patches of lodgepole pine
on lonely buttes in South Dakota,
and more recently in the range
country of western Nebraska.
You can find nesting saw-whets in
the mountains outside Los Angeles, and my colleague Juan Pablo
Medina is studying the southernmost breeding population on the
15,000-foot-high Toluca Volcano
near Mexico City.
We’ve learned a lot, but there’s
still so much we don’t know
about these birds. We don’t know
how their population is faring,
although with a number of long-term data sets like ours we can
begin to look at whether their
numbers are stable or changing.
We can look at whether the timing
of their migration is shifting due
to climate change.
One big remaining gap is our
continued inability to observe
saw-whet owl migration directly,
however. Almost everything we
think we know about their migra-
tion is inferred from capture rates;
they are too lightweight for all
but the tiniest tracking devices, so
we know little or nothing about
flight speed, altitude, and stopover
length, among many other things.
We don’t know whether they fol-
low forested ridge systems like
diurnal raptors, or fly in a broad
front across the landscape like
other nocturnal migrants.
These questions are of more
than academic interest; I routinely
receive inquiries from wind-energy
developers wanting to know the
answers to these questions in an
attempt to avoid conflicts with
turbines, but so far, our ignorance
outstrips our understanding.
We’ve used nanotag transmitters
to plot their regional movements,
and we even tried marrying verti-
cal-beam marine radar with infra-
red video cameras to find, identify,
and follow saw-whets passing
overhead in the dark—an experi-
ment that didn’t work quite well
enough to answer our questions.
But we keep trying. What started for me as a fun date has turned
into an obsession, one that has
robbed me of plenty of sleep, but
has paid ample dividends in excitement and discovery that more
than make up for the tiring nights
each fall. a
Author and researcher Scott
Weidensaul’s latest book is the
Peterson Reference Guide to
Owls of North America and the
Caribbean. See page 127.