Editor’s note: Brandon Caswell has been fascinated in natural history since he was 5 years old. He has undergraduate degrees in biology, anthropology and geology. He enjoys bird-watching and nature photography. His current studies center on Precambrian and Archean rocks from Ellesmere Island, Canada. He also helps instruct introductory and advanced courses in environmental science and geoscience at the University of Iowa. He lives in Marion with his wife and son.
By Brandon Caswell, correspondent
One of nature’s great spectacles is the irruption of Snowy Owls from the far northern reaches of North America to Iowa and the Midwest.
Scientists studying these magnificent birds believe both the shortage and surplus of their staple prey item — the lemming — is responsible for sending hundreds of them far south out of the Arctic and subarctic in search for food.
This winter is one of those occasional irruption years and appears largely due to the abundance of prey resulting in a spike in reproductive success during the breeding season.
The Iowa Ornithologists’ Union, the state bird-watching organization, has a map on their website (www.iowabirds.org/) showing reported Snowy Owl sightings in Iowa so far this winter season.
The Snowy Owl is large, similar in size to the Great Horned Owl, and comes in a variety of color patterns. Many are not the prototypical all-white Hedwig of Harry Potter fiction, but are heavily marked with dark barring. Many of the Snowy Owls noted across Iowa this winter are heavily barred juveniles representing both sexes. Adult females are less barred than juveniles, while adult males can be nearly pure white.
The vast agricultural lands of Iowa offer Snowy Owls a similar habitat to their treeless Artic tundra. In fact, Snowy Owls are unfamiliar with trees and prefer to sit atop poles or other human structures. They also tend to sit in plowed fields, making them incredibly hard to see if snow is on the ground.
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One of the best ways to find them is to visit rural, open agricultural areas and scan the tops of all visible utility poles with binoculars. Make sure to check fields for sitting owls, although this can take great patience and luck.
Approaching Snowy Owls can be tricky. Etiquette should be used in all scenarios. Staying in a vehicle is recommended. Using your vehicle as a blind can greatly benefit your chances for a good photo. Recognizing the owl’s body language is the best way to judge a comfortable distance. An attenuated owl with attention fixated on the human observer is probably too close. Sometimes owls will rock forward or defecate, which also are signs to back away.
Keep the owl’s safety in mind. An owl perched on a sign or utility pole near a heavily trafficked area should be respected in the utmost.
By winter’s end, Snowy Owls will migrate back to their northern breeding grounds. Until then, enjoy them while keeping their well-being in mind.
Other wintering birds to look for in February:
l Raptors, including wintering Rough-legged Hawks, from the north in open country areas and Bald Eagles, which often concentrate along open stretches of water, such as the roller dams in Cedar Rapids and Iowa City, or the lock and dams along the Mississippi River.
l Gulls feeding along open water during the day and roosting on the ice after feeding.
l Snow Buntings, Lapland Longspurs and Horned Larks; small birds that often are flushed from the sides of gravel roads.
l Feb. 15 — Iowa City Bird Club monthly meeting. Mark Brown presents “Wildlife of the Smoky Mountains” http://icbirds.org/eibarchives/17Dec.pdf
l Feb. 18 — Quad Cities area for gulls, waterfowl and other birds on the Mississippi River. http://icbirds.org/eibarchives/17Dec.pdf
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In sunny conditions overexposing is a problem. This means the image will be too bright and loses detail. Avoid underexposing by dialing your camera’s exposure compensation amount to a negative value (e.g. -1). Use high shutter speeds with shutter priority settings in sunny conditions. In lower light, an aperture priority setting is recommended. A tripod or monopod also can be helpful in obtaining a crisp photo in low light.
l Email email@example.com with comments and Eastern Iowa bird-watching events