Endangered Species Report #53 The Eastern Screech Owl: Our Nocturnal Neighbor
Jumat, 22 Februari 2013
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Endangered Species Report #53
The Eastern Screech Owl: Our Nocturnal Neighbor
Written by: Holly Koppel
The Eastern
Screech Owl was discovered and named in 1758 by the Swedish naturalist, Carolus
Linnaeus; however, the Screech Owl had been known for years by various folk
legends, most notably the Choctaw Indian legend. The Choctaw Indians say that
if a screech owl was heard, a child under seven would die. Other variations of
this legend say that just to hear the call of a Screech Owl means that someone
(not necessarily a child) will die. These legends might stem from the fact that
the call of the Screech Owl is a mournful sound that people would associate
with death, but these are mostly folk legends and we know that these owls are
nothing to fear.
In fact, the
Eastern Screech Owl is one of the most common owls in the United States as they
have adapted very well to the suburban environment. Their range goes throughout
North America, from the Rocky Mountains in the west to the Atlantic coast and
through Florida to southern Texas. Their habitat is quite diverse and includes
coniferous forests, cottonwood bottoms, boreal forests, and urban environments.
They are generally found in wooded areas, but have adapted well to urban and
suburban areas and often use bird boxes for nesting.
The Eastern
Screech Owl is also one of the smallest owls in North America. The average size
for a female Screech Owl is 9.2 inches in length and 7.3 oz in weight. The
males are a bit smaller, averaging only 8.2 inches in length and 7 oz in
weight. Their wingspan is about 19-24 inches. These owls are also dichromatic,
meaning that they have two distinct color morphs, either uniformly gray or red.
Both color morphs make it difficult to see the owl when they are sitting in a
tree as they will tend to blend in the with the surrounding bark. The owls also
have have bold streaks on their breasts, yellow beaks and eyes, large feet with
feathered toes, and large ear tufts on either side of their head that they can
have stand straight up or they can put the tufts down.
These owls
hunt at night, mostly from dusk until dawn, with most of their hunting done
during the first four hours of night. They will hunt mainly in flight in open
woodlands, along edges of open fields, or in wetland areas, although sometimes
the owls will hunt by sitting on a tree branch and waiting to see or hear prey.
They have excellent hearing and can hear prey hidden under leaf litter. Their
diet consists of insects (like moths and katydids), crayfish, earthworms,
reptiles and amphibians, small mammals like mice and bats, and songbirds.
Mating
season for the Eastern Screech Owl begins in March and the owls nest in natural
cavities in trees, old woodpecker holes, or bird boxes. Courtship between owls
involves the males bowing, raising wings, clicking their bill or bringing food
to the female. Eastern Screech Owls mate for life and mated pairs can be seen
preening each other's feathers and calling in duet. Their call is a muted trill
made mostly by the males; however, they also use a "whinny" call
during courtship.
The female
Eastern Screech Owl will typically lay about 2-7 eggs per clutch and they will
lay the eggs over a period of days (sometimes up to a week) and do not begin
full-time incubation until the last egg is laid. Incubation for the eggs is
about 26 days; however, because of the delay in laying eggs, sometimes the eggs
laid first will develop and hatch first.
When the
young are born, both parents will feed them; however, the males are primarily
responsible for feeding the females and guarding the nest cavities against
predators. Predators for the owl include Black Rat Snakes, Virginia Opossums,
and Raccoons. The owl will use alarm calls and will physically attack predators
that approach their nests and fledglings. Also, while the owls are nesting, the
adults will sometimes bring back small, worm-like Blind Snakes and release them
into the nest. These Blind Snakes will burrow into the nest and clean out any
insects and will help to protect the young against parasites.
The young
owls will leave the nest at about 28 days old and will then remain with the
parents until they are 8-10 weeks old. During this time, both parents will
continue to feed the young. Once the young leave to stake out their own
territory, the parents will split up again until mating season the next year,
and then may re-use the same nest site.
It is fortunate
for these owls that they have learned to adapt to humans so well; as a result,
they are not facing the same plight that their cousins the Spotted Owls are,
and the fate that Burrowing Owls and the Barn Owls will soon be facing. One of
the best ways to help the Eastern Screech Owl is by building and putting a
Screech Owl box in your backyard! Fred Gehlbach, known as the world's leading
authority on Screech Owl behavior has tried some variations on nest boxes and
found that the birds tend to use deep cavities, more than 10 inches deep, with
entrance holes not much larger than the minimum needed for their own entry. He
also discovered that if the floors were only six inches across, young owls
would sometimes fledge early and that would lead to crowded nests, and so he
concluded that boxes with floors that were eight inches square were the perfect
size.
There is
some disagreement about whether cleaning out nest boxes yearly is helpful for
Screech Owls. Since the Screech Owl tends to put Blind Snakes in their nests,
you might find more than you bargained for when trying to clean one out! If you
do decide to put up a Screech Owl box, make sure that it is at least 12-20 feet
off the ground and in deep shade. Try to place the box away from sidewalks or
doors since these owls are very good at protecting their nests and have been
known to bother people who come too close to them.
So, despite
the fact that humans are continuing to encroach on the Screech Owl's natural
habitat, there are things we can do to help them adapt to our presence.
Educating people about Screech Owls and dispelling any erroneous information is
important, and so is giving the owls a place to nest. If we can help educate
people and provide nest boxes for Screech Owls, then we will be able to enjoy
these nocturnal birds for many years to come.
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Eastern
Screech Owl
Kingdom:
Animalia
Phylum:
Chordata
Class:
Aves
Order:
Strigiformes
Family:
Strigidae
Gennus:
Otus
Species:
Otus Asio
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