Late in December, a birder reported seeing three snowy owls at Minneapolis/St. Paul International Airport. This was exciting, because it's a rare treat to spot one of these spectacular white owls. And such sightings inevitably make the birding community hungry for more — for a winter when many snowy owls show up in our state (more about that later).

Snowies are well-named, with striking white plumage that blends well with snowy backgrounds. Because they hatch and spend much of their lives in the Arctic, they're not daunted by cold or wind-swept landscapes. In the Arctic they hunt for lemmings, but when far from home they survive on mice, rats and rabbits, as well as birds and ducks, sometimes even a great blue heron. Once they're on the move they often settle at Arctic-looking places, such as airports and open fields.

These big owls measure about 24 inches from their heavily feathered feet to the tops of their big, round heads. The ones in our area left the tundra late last fall, migrating southward to spend the winter, with early reports coming from the shores of Lake Michigan in November.

While a few snowy owls are reported in Minnesota most winters, birdwatchers always hope that each year will be an "irruption winter," when a flood of snowies appears in our region. This doesn't happen often, but some are already predicting that this will be one of those winters.

Despite their affinity for airports, these can be dangerous places, both for the birds and for aircraft, if an owl collides with a plane. No one knows this better than Norman Smith, who has spent 40 years capturing and relocating the snowy owls that settle in at Boston's Logan International Airport each winter. As the director of a major Massachusetts Audubon nature sanctuary, he helped develop a system for trapping and banding the owls and then releasing them, a feat that requires many federal and state permits.

"In an average winter, I relocate 15 to 20 owls," Smith says, "but the big year, 2013, I relocated 121 owls from Logan." He captures and takes the owls either to coastal salt marshes or to areas north of the airport, both good hunting grounds. Smith, who has relocated 20 owls so far this winter, adding to his total of 900 owls banded over 40 years, has retired from his day job.

At our own international airport, the staff first uses noise-makers and fireworks-like bursts to try to drive the owls away. If these don't do the job, the owls are captured and relocated.

The big question is why do snowy owls irrupt, flooding southward in some years, occasionally appearing as far south as Florida? The theory used to be that snowy owl irruptions were driven by a scarcity of Arctic lemmings, the owls' dietary staple. This was partly based on the experience of rehabilitation centers, which admitted many starving snowy owls in irruption years.

The picture now looks more complex, based on information from researchers studying these owls in the field and from banders like Smith: In summers when lemmings are abundant in the Arctic, snowy owl nests produce a large number of youngsters. Once these juveniles fledge, they push out to find their own feeding territories, some eventually reaching our region.

Researcher J.F. Therrien, who studies the owls in the Arctic, says snowies disperse across the tundra every year in search of lemmings. "They're not starving, 80 percent or more are in quite good shape in winter," Therrien stated in a recent International Owl Center webinar.

Whether or not this turns out to be a year with high numbers of snowy owls in Minnesota, spotting even a single bird is a treat.

Because they're so spectacular, and are not seen every year, reports of snowy owls tend to bring out crowds of people, and this can be a problem. If humans approach too closely, owls can be spooked into flight, becoming vulnerable to traffic or predators. Snowies tend to rest in the daylight hours, and hunt at night, so continual daytime disturbance can be a major stress. Please note the box with tips for respecting their space.

St. Paul resident Val Cunningham, who volunteers with the St. Paul Audubon Society and writes about nature for local, regional and national newspapers and magazines, can be reached at valwrites@comcast.net.

Don't stress 'em out

Snowy owls often draw a crowd. Here are tips for allowing these beautiful visitors to hunt and rest without disturbance and to respect private property:

Do not approach an owl; it's best if you stay in your vehicle.
If you do get out, stay at least 50 to 100 yards away.
Use binoculars or a scope to bring the bird in closer.
Remain quiet so you don't spook the owl.
Don't leave food for the owl.
If the owl is on private property, don't enter without permission.

More about the snowy owls

Male snowy owls show dark brown feather barring when they're young and become whiter as they get older. Females keep some dark markings throughout their lives.

Study flat areas and watch for any irregularities in the snow — a lump or dirty patch could be a snowy owl facing away from you. These owls often perch out in the open, so check high points like hay bales, fence posts, telephone poles, buildings or grain elevators.

Snowies' thick feathers provide protection from Arctic cold and make them North America's heaviest owl, weighing about 4 pounds. Great horned owls, another large owl, weigh about 3 pounds.

Snowy owls make distinctive sounds (allaboutbirds.org/guide/Snowy_Owl/sounds).

Some resources:
International Owl Center, Houston, Minn.: internationalowlcenter.org
Project SNOWstorm: projectsnowstorm.org
Owl Research Institute, Charlo, Mont.: owlresearchinstitute.org
All About Birds, Cornell Lab of Ornithology: allaboutbirds.org/guide/Snowy_Owl

Some stats
Females are larger than males
Length: 20.5 to 27.9 inches
Weight: 56.4 to 104 ounces
Wingspan: 49.6 to 57.1 inches
Nests on the ground