Zoo Tales: Owls Are Raptors Too
BY TOM GILLESPIE
Special to The Pilot
With their small bodies and long, slim legs, it's sometimes hard to think of burrowing owls (Athene cunicularia), the newest bird species at the North Carolina Zoo, as raptors (or birds of prey), but that's what they are - just like hawks, falcons, eagles, ospreys and a few other birds of prey species.
Found throughout the open landscapes of North and South America, these ground-dwelling owls get their name from their habit of nesting and roosting in burrows, particularly those excavated by small mammals and large reptiles.
Unlike most owls, they're often active during the day. But they still tend to do most of their hunting from dusk until dawn in order to use their night vision and hearing to their advantage.
In North America, they can be found across the Canadian grassland regions of southern Alberta, Saskatchewan and Manitoba. They occur in all states west of the Mississippi Valley.
A separate subspecies is found in Florida and the Caribbean islands. They extend south into Mexico, Central America and South America. Their populations from the northern parts of the U.S. and Canada migrate.
Averaging about 10 inches high, weighing about six ounces and with a wingspan of only about 20-24 inches, they're much smaller than most owls. And unlike most owls in which the female is larger than the male, the sexes of the burrowing owl are the same size.
Their diet in the wild is primarily insects, mammals, birds, and small reptiles and amphibians.
Burrowing owls, like all owls, meet the three necessary requirements to qualify as birds of prey: strong taloned feet, a hooked upper beak for tearing prey into pieces, and excellent eyesight.
Raptors' eyesight is unequaled in the animal world. An eagle, for example, has eyesight about nine times better than a human's. The eyes of most owls are so large, relative to their body size, that there is no room in the skull cavity for eye muscles. To compensate for this lack of eye movement, the owl is able to rotate its head about 270 degrees. To accommodate this movement, the owl has 14 vertebrae in its neck, as opposed to seven in a human. If an owl's head were the size of a human's, its eyes would be the size of softballs.
Equally impressive are the owl's specially adapted wings, which allow almost noiseless flight due largely to their ability to fly slowly with relatively little beating of their wings. This silent flight helps them listen for the scurrying of their prey and also reduces their chances of being heard by the prey as they approach.
Their ability to fly slowly is due, in part, to the high curvature or "camber" of the wings, which allows each wing beat to produce more lift. The fine, feathery edges of each wing also reduce any loud turbulence, adding to their silent flight. Friction noise between single feathers is reduced by their velvety surface.
Current population estimates of burrowing owls are not well-known, but data suggests significant declines across their range. Most experts estimate that there are fewer than 10,000 breeding pairs in the wild.
Particularly in the large farming areas of the U.S., burrowing owls are threatened by agricultural development and the use of pesticides and efforts to eradicate prairie dogs, which typically live in the same terrain as burrowing owls. Droughts pose even more problems for them through reduced nest success and greater frequency of fires.
Owls, like all raptors, are high on the food chain and have few predators - except the one that could cause their most rapid decline: man. In the wild, their natural predators include hawks, foxes, badgers, domestic pets and even larger owl species.
Because of the growing concern over dwindling numbers of burrowing owls, some conservation groups have begun petitioning states to list the owl under the states' endangered-species acts. Fortunately, it's not too late to save these birds, but it is essential that we all develop a more concerned attitude and tolerance for all the wild creatures that share the Earth with us.
Zoo visitors can also see a female barred owl at the Streamside exhibit in addition to the two new burrowing owls at the Sonora Desert exhibit.
Tom Gillespie works in the public affairs office of the N.C. Zoo.
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