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Snowy owl sightings: Experts offer explanation for mass migration

Snowy owls headed south in record numbers over the recent winter, to the delight of birdwatchers from Vermont to Wisconsin to Washington state, reports Science News on Sunday, April 13. But the large increase in the number of flying visitors from Canada, Alaska, and the Arctic should not cause watchers any concern. It’s all about the supply and demand in the owls’ food supply.

The increase in sightings of the beautiful birds stretches as far as Tennessee. There have even been unusual sightings in South America. And the reason, report scientists, has to do with the small mammals the large birds live on. Snowy owls are raptors – not the kind of visiting birds that put away seeds from local bird feeding stations. They prefer lemmings, which are small rodents which live in cooler climates. But if the lemming supply runs short, the owls need to move south in search of prey.

It can work two ways: There seem to have been a record number of lemmings available a year ago, so record numbers of owl eggs hatched baby birds. Then, with more adult birds available to eat them the next season, there were not enough of the mousy creatures to be found. That is almost certainly why the birds migrated in record numbers. A lack of food supply is usually the cause of shifts in animal populations.

As CBS station WTVR reports, “It’s actually pretty special to have snow owls in New Jersey,” said US Fish and Wildlife Service spokesman Donald Freiday last December. “We normally in a given winter will have between none and three. This year, the whole state there are as many as 30.” From three to 30 is quite a jump.

And people armed with cameras followed them on their southward journey, from bird-watching sites such as Grays Harbor in Washington and Atlantic City in New Jersey. And the cameras are still in place to follow the mass migration home to the Arctic, as spring sets in. The competition for food keeps snowy owls on the move. And the search for great pictures has the same effect on humans.