Biology Reference
In-Depth Information
Owls, even large species, subsist mostly on small mammals such as mice, voles, and lemmings.
These are promptly gulped down whole, and then another adaptation—their unusual digestive sys-
tem—takes over. Indigestible parts, such as bones and fur, are packed together into pellets by stomach
action, then are regurgitated, thus efficiently ridding the owl of useless material. An owl's favorite
roosting place can sometimes be identified by the pellets beneath it. These pellets can also tell us much
about an owl's food habits. By dissecting and analyzing pellets, researchers can determine what species
an owl has been feeding on.
Collectively, owls are properly known for their hooting, but most people fail to realize that they
make a wide variety of other sounds—and that some species don't hoot at all. Many strange nighttime
noises, and some during daylight hours as well, are often attributed to various other creatures, when in
fact they emanate from the vocal apparatus of owls. Yes, some owls do give a hoot, but this is by no
means their universal language.
At least eighteen species of owls are found in the United States and Canada. Several of these,
however, such as the elf owl and ferruginous owl, are found mainly from the southern part of Mexico
and barely come into the United States. It's beyond the scope of this topic to attempt a description of
every species and its habits, but let's take a close look at several of the more widely distributed and
interesting owls.
THE BARRED OWL
The barred owl
(Strix varia)
is the most common large owl in the eastern United States, ranging to
roughly the Mississippi River and considerably farther west in southern Canada. Its range also extends
northward to the southern tip of Hudson Bay. This is also the most commonly seen owl because it's
often quite active in the daytime, especially in the late afternoon. Named for the horizontal bars across
the upper breast and the prominent vertical brown streaks down its belly, this owl is easy to identify
because of its big, liquid brown eyes and lack of ear tufts. (The barn owl is also “earless,” with brown
eyes, but is much smaller and has a heart-shaped “monkey” face.) In contrast to the fierce yellow eyes
of most owls, the barred owl's big brown eyes lend it a deceptively benevolent appearance.
With its puffy head and a wingspan of three and a half feet or more, the barred owl is an imposing
bird. Among owls commonly resident in the United States, only the great horned owl is larger; in
Canada, the great gray and snowy owls are larger, as well. Still, the barred owl's size isn't far inferior
to that of those other species, and anyone who has had a close view of one would certainly describe it
as a large owl.
Despite its rather impressive height and wingspan, the barred owl can serve as Exhibit A in docu-
menting why owls in general aren't what they appear to be. Beneath all those feathers, there's remark-
ably little bird: even a large barred owl weighs only about two pounds, and most are probably closer
to a pound and a half or less! There's a purpose to all those fluffy feathers, though: they serve the dual
