MADISON, Wis. (AP) — Wisconsin hasn't seen the increase in the number of snowy owls this winter that have visited the state in recent winters from their usual nesting grounds above the Arctic Circle.

Many more of the white birds than normal visit some years, creating what the Wisconsin Department of Natural Resources calls an irruption, Wisconsin Public Radio (http://bit.ly/2lYjR29) reported.

Nearly 240 snowy owls were reported in the winter of 2014-15, and nearly 250 were spotted in 2015-16. Department officials say this winter's more than 50 owls is a more standard number.

Karla Bloem, executive director of the Houston-based International Owl Center, said researchers used to think this happened because of a lack of food in Canada, but that doesn't seem to be the case anymore.

The traditional thought was that when you have snowy owls coming south, it's because there's not enough food up in Canada, and everyone is starving, and they come south," Bloem said. "(But) they realized that a lot of the birds that are coming south are fat and doing well."

She said the latest research has shown that it's probably because of the stability of food in Canada. She said climate change should also be considered when studying snowy owls' migration patterns.

"The tundra is a pretty fragile habitat, and of course the lemmings that live there (a major source of food for snowy owls) are very dependent on the vegetation there, which is dependent on the climate, and the snowy owls are dependent on the lemmings," she said.

___

Information from: Wisconsin Public Radio, http://www.wpr.org