Transcript of tomorrow's For the Birds
This week I went to one of my favorite Duluth birding spots,
along the Western Waterfront Trail, with my son Tom. While we were walking
along, we suddenly both heard a woodpecker drumming very rapidly, with an oddly
metallic quality. The rapidness of the drumming made me think it must be a
Hairy Woodpecker, and the metallic quality told me this bird was not drumming
from a tree but, rather, on a manmade structure. Sure enough we found the bird
hammering out its territorial drumbeat on a metal clip on a power pole.
Woodpeckers try to find the most resonant structure within their
territory--drumming on that will make their voice carry farther, both to
communicate with their mate and to defend a larger territory.
Even though Hairy Woodpeckers are larger, they drum faster
than the littler Downy Woodpecker. I can recognize them by the fast rhythm with
about 90 percent accuracy, though I must admit it took me a long time and a lot
of practice to do this.
Hairy Woodpeckers are a common species found throughout most
of Canada and 49 states down to Panama and the Bahamas. In some areas they
focus on pine trees, but over most of their range they’re found in a wide
variety of forest types.
Common as Hairy Woodpeckers are, they’re inconspicuous
during the point in their nesting period when parents are incubating. So of our
common resident birds, this is the species most often missed on Big Days in
Wisconsin and Minnesota in late May and early June.
Hairy Woodpeckers are often drawn to the drumming sounds of
Pileated Woodpeckers, and often follow them when feeding. A Pileated can dig
into trees far deeper than a Hairy Woodpecker can, and after the Pileated moves
on, the Hairy can dig out bugs it could never have been able to get on its own.
To minimize the work involved in digging out larvae within wood, woodpeckers
that probe for bugs in trees have a stiff, barbed tip to their extensible
tongue. They can dig in to where they can touch a grub and then extend the
tongue to hook into it and pull it out.
Hairy Woodpeckers often mate for life. During winter, when
they do best in isolation, they apparently still maintain auditory contact with
their mate. Up here, when they dig out a nest or roost cavity, they seem to
prefer living aspens with heart rot fungal infections that make hollowing out a
nest chamber easier.
Like other woodpeckers, Hairy Woodpeckers have smaller eggs
relative to body size than other kinds of birds, with a relatively shorter
incubation period as well. This is probably because oxygen exchange within eggs
is tricky enough without being in a cavity where carbon dioxide builds up and
the atmosphere gets very close, especially at night while the incubating parent
hardly moves all night. The chicks hatch at a less developed stage than most
hatchlings. The parents flying in and out to feed them promotes oxygen
exchange, and as soon as they can, the chicks start spending much of their time
up at the nest entrance where they can get plenty of fresh air.
Woodpecker
chicks are shockingly noisy, begging for food much of the day in such a loud
way that it seems surprising more aren’t lost to predators. Fortunately, their
system works for them and so Hairy Woodpeckers are here to stay.
