Fall's Journey South Update: October 16, 1998
Today's Report Includes:
Shhhhh! Top Secret Birds!
Every year in October, tiny owls are astir throughout much of Canada and the United States. Saw-whet Owls spend
the winter throughout the lower 48 states except near the Gulf coast, with at least a few remaining in their nesting
grounds in Canada and the northern states even as others migrate south. So every fall, winter, and spring it's
possible to see them in most places of the U.S. and Canada.
Journey North's Elizabeth Donnelly meets a Saw-whet Owl
If they have such a wide range, why is it that most people live their entire lives without ever seeing one of these
adorable little raptors? Mostly it's because they're so secretive. To help achieve silent flight, owls have slower-beating
wings than hawks their size, so they're easy for hawks to catch. Large owls don't worry about hawks because they
can fight back effectively, but saw-whets and most other tiny owls are strictly nocturnal in part so they won't
be out and about when hawks are active. Even at nighttime they must be very secretive, because they are also prey
for bigger owls. So they spend their lives hiding out.
Owls Keep Scientists in the Dark
In order to learn anything about such secretive, nocturnal birds, the scientists studying them must work at night.
Most of what we know about Saw-whet Owls comes from banding studies conducted in spring and fall when owls are
migrating. The banders set out fine mist nets which the owls can't see in the dark. If an owl flies into the net
it gets tangled and becomes stressed, so the banders must check nets frequently throughout the night. If the weather
gets too bad to go out, they take the nets down. Banders catch at least some owls just setting their nets out where
the owls happen to be migrating, but to maximize the number of owls caught, they often play recordings.
(Recording of a Saw-whet Owl courtesy of Lang Elliott.)
Migrating Saw-whet owl during a brief midnight visit at the banding station.
If a bander or assistant finds a Saw-whet in a net, s/he must be very careful untangling it because
like other birds, these tiny owls have hollow bones which are easy to break, and like all raptors, they have dangerous
feet. It's tricky working in the dark, so banders wear a head lamp. They free each owl from the net and take it
inside to the banding station to be measured and banded. They determine its sex by how big it is (female hawks
and owls are always bigger than males). They estimate the age by the color of the beak (a pale beak tip indicates
an owl that was hatched this year) and by the condition of the feathers (an owl with all new feathers was hatched
this year). Saw-whets molt their wing feathers in a special order. Looking at which parts of the wing are worn
and which are new can sometimes give a rough estimate of the owl's age.
Right now we are at the peak of Saw-whet Owl migration in the Great Lakes region. Near Lake Michigan, at Little
Suamico Ornithological Station in Oconto County, Wisconsin, banders had netted 184 owls this fall as of October
14. Ten of these were owls that already had a band, either from the same station in previous seasons or from some
other banding station. At Linwood Springs Research Station, near Stevens Point in central Wisconsin, a total of
75 saw-whets were caught between September 21 and October 10, 1998.
A Closer Look at Banding
Journey South visited one Great Lakes banding station near Lake Superior, at Hawk
Ridge Nature Reserve in Duluth, Minnesota. Elizabeth Donnelly and Laura Erickson ventured out on October 2,
1998, arriving in the "half shack" (named because it's so tiny) about 9:30 p.m. We were greeted by Dave
Evans, three assistants, and a couple of Saw-whet Owls waiting to be banded.
Marking the flight feathers.
While Dave explained how owls are trapped and aged, his helpers showed us how they measure the wings and mark the
feathers. The flight feathers on one wing are each marked with a green marker, which brings us to this week's
Challenge Question #7: "Why does Dave Evans mark owl
flight feathers with a permanent marker? And how long will these markings last?"
To Respond to Challenge Question # 7 please follow the
instructions at the end of this report.
Gone with the Wind
We accompanied the banders as they checked the nets a few times over the next two hours, and watched them deal
with five of these little owls. It was windy, reducing the number of owls caught. We asked Dave why few owls are
caught during windy conditions. Was it because they don't like to migrate in the wind? He said probably not. He
thinks it may be because the owls can hear the nets shaking in the wind and avoid them. Seeing five owls this closely
was so exciting that we can't even imagine what it would have been like the next week. On the night of October
7-8,1998, Dave caught 135, and the night of October 13-14 he caught another 115! (To hold so many owls, the banding
station is equipped with tiny mailboxes the scientists call "saw-whet condos".)
JN's Laura Erickson holding a Saw-whet Owl.
It was such fun watching the banding that sometimes it was hard to remember that this is serious business. Although
sometimes birds are accidentally injured or killed while being netted or handled at banding stations, Hawk Ridge
has one of the finest safety records of any banding station in the country because of the careful and gentle way
Dave goes about his business. Like most banding stations, Hawk Ridge doesn't normally allow visitors--it's too
easy to make a mistake when talking or showing banding procedures. So we felt honored that Journey South was allowed
to observe this exciting and interesting activity.
Discussion of Challenge Question #6:
In last week's report we asked you to consider this puzzling fact: "The weight of adult male loons in Maine
averages heavier than 6000 grams, while loons from Michigan and Wisconsin average only about 4500 grams. Wings
are about the same size on each. What might be one explanation for that huge difference in body size?"
One Journey South participant named Mike explained, "The loons farther away have less weight to migrate
with. [That's] the good part about not weighing a lot....they have a longer flight."
In fact, loons from Maine may only migrate a hundred or so miles, while those from Michigan and Wisconsin have
to fly several times as far to reach the ocean. Having lighter bodies reduces their "wing load," making
this long journey easier.
How to Respond to Today's Challenge Question:
1.Address an e-mail message to: email@example.com
2.In the Subject Line of your message write: Challenge Question # 7
3.In the body of the message, answer the Challenge Question.
The Next Journey South Update Will Be Posted on October 23, 1998
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