Lake Andes: A species of majestic, mostly white owls famous for its role as Harry Potter's companion in the books and movies is being sighted in abundant numbers this winter far from both Hogwarts and its native Arctic habitat.

It's typical for snowy owls to arrive in the US every three or four winters, but this year the birds have been witnessed in large numbers. Birders from the Pacific Northwest to New England reported frequent sightings of the yellow-eyed birds. As many as 30 were spotted in December around South Dakota's Lake Andes.

"Thirty in one area, that's mind numbing," said Mark Robbins, an ornithologist with the University of Kansas Biodiversity Institute.

The arrival of the birds, which can top 2 feet (0.6 meters) in height with a wingspan of nearly 5 feet (1.5 meters), is the result of a plentiful population of Arctic lemmings this summer, which led to a strong breeding season, said Denver Holt, director of the Owl Research Institute in Charlo, Montana.

Lemmings are snowy owls' main food source, and the baby boom is sending many of the youngsters across the border to scrounge for voles, field mice, rats, rabbits and shore birds.

"It's very unusual, because it's coast to coast," said Holt, who has been researching the owls' Arctic habitat for 25 years.

Snowy owls are drawn to frozen lakes, which remind them of their tundra back home in the Arctic, Robbins said.

"And if they're finding rodents there, they're staying there," he said. "And perhaps seeing a couple of more snowy owls there, they may think, 'OK, this is a hot spot.'"

The owls have been regular visitors to Boston's Logan Airport, and one even showed up just after Thanksgiving in Hawaii. Chicago's Montrose Point Bird Sanctuary has become a haven for the creatures, with "countless sightings" this season, said Matthew Cvetas, an Evanston, Illinois, birder.