February 20, 2014

She was only one of the more than 2,500 snowy owls that left the Arctic for the United States and Canada this winter. But thanks to an encounter with a city bus and an SUV, she became a media star. On January 30, the owl, which had appeared in Washington, D.C., some days earlier, suffered a broken toe and a head injury in a traffic accident. Rushed to a city wildlife facility, she was treated successfully and moved to comfortably cold rooms for her recuperation. Apparently, she enjoyed the food—white mice—served at the facility. But as she improved, she became increasingly dissatisfied with her small accommodations. So earlier this week, her caretakers moved her to larger quarters at an undisclosed location. Bird experts there hope she will be healthy enough for release in spring, when snowy owls traditionally return to the Arctic.

Snowy owls are graceful birds of prey that usually live on the Arctic tundra in Canada, where they feed mainly on lemmings. The owls reach about 23 inches (58 centimeters) long and have mostly white plumage with brown markings. Adult females have more brown markings than the adult males.  In addition to lemmings, the owls may feed on mice, voles, ducks, and hares.

The call of the snowy owl features several rough notes and sounds somewhat like a dog’s bark. (Alan D. Carey, Photo Researchers)

Although snowy owls migrate south every winter, this year’s invasion has been one of the largest in memory, scientists said. Bird watchers working with eBird, an online citizen science project run by the Cornell University Lab of Ornithology and the National Audubon Society, have reported spotting the owls in 25 states and 7 Canadian territories. The project (at ebird.org) uses sightings collected by bird watchers in more than 115 countries to create maps showing where species can be found. Unlike most owls, snowy owls are active during the day, making them easier to observe. Usually, the younger birds make the trek south, chased out of their home range by older birds after fresh snow starts to fall. The lemmings take advantage of the cover to drop out of sight, significantly reducing the food available to the owls.

Additional World Book articles:

• Audubon, John James
• Bird
• Spotted owl

Jan. 25, 2012

Snowy owls have been descending on the northern United States this winter by the thousands, to the delight of bird watchers and scientists. These graceful birds of prey usually live on the Arctic tundra in Canada, where they feed mainly on lemmings. Normally, only a relatively small number of the owls migrate south in the winter. The owls have also spread out farther than usual, appearing from the Atlantic coast to the Pacific and as far south as Kansas. One owl even reached Hawaii, where authorities shot it out of concern it would interfere with aircraft. Such a rapid increase in the numbers of a bird in an area where it is not usually found in winter is called an irruption. Scientists have been tracking the locations of the birds with great precision thanks to a citizen science project called eBird. Run by the Cornell University Lab of Ornithology and the National Audubon Society, the online project (at ebird.org) uses sightings collected by bird watchers across North America to create maps showing where species can be found.

Unlike most owls, snowy owls are active during the day, making them easier to observe. The owls reach about 23 inches (58 centimeters) long and have mostly white plumage with brown markings. Adult females have more brown markings than the adult males. The owl’s call features several rough notes and sounds somewhat like a dog’s bark. In addition to lemmings, the owls may feed on mice, voles, ducks, and hares.

Female snowy owls have more brown markings than the males do. Alan D. Carey, Photo Researchers

Scientists are not certain why the owls have migrated south in such numbers. However, many animals in northern regions follow a boom-and-bust population cycle. For example, lemmings quickly grow in numbers when there is abundant vegetation. A boom in the population of lemmings provides abundant food for snowy owls. However, the lemmings soon eat much of the available food, and their numbers plunge. At that point, there may not be enough lemmings to support the large number of snowy owls. These conditions may cause snowy owls to fly farther south than usual, as they seek other sources of food. The irruption is expected to end by March or April.

Additional World Book articles:

• Audubon, John James
• Bird
• Spotted owl