Many of the snowy owls that migrated south to Kansas likely won't make it back home to the arctic tundra.

"These guys have to run a gauntlet to get back to where they came from," said Mark Robbins, the ornithology collections manager for the University of Kansas in Lawrence.

He's the person who has been receiving most of the Kansas and Missouri snowy owls that have already died this winter.

Even those falling victim to cars, trucks, electrocution and even trains have been underweight, in some instances markedly so.

So far, Kansas has had a minimum of 131 confirmed sightings this year, he said. Missouri has had about 60.

Robbins, however, has already received the bodies of 20 owls from Kansas and Missouri that died for one reason or another.

"That's the one that were found," he said.

While it's uncommon for snowy owls to venture as far south as Kansas, it's not unheard of. The last time, however, was the invasion of 1974-75, a time, Robbins said, when no one had cellphones and the Internet didn't exist.

But as this year's invasion grew, he and others put out the word to see how it might compare to nearly 40 years ago.

"I think they may be comparable," he said of the 81 owls that were reported from 1974-75. "This is certainly on the same magnitude."

The migration this year is believed to be a result of a burgeoning population of snowy owls and a collapse in the lemming population, a key part of the owls' diet.

In Kansas, the birds have feasted on the meadow vole, similar to lemmings. But they've also eaten other birds.

But as the birds headed south, the flight has taken its toll.

Birds that should normally weigh 1,800 grams are now weighing 900 grams, Robbins said.

Even birds appearing to be healthy are weighing less than they should, as the struggle to survive ultimately starts robbing the animal of its health -- losing muscle and moisture just to live.

The same is being seen in Nebraska where the number of birds is even higher.

He's not optimistic about the birds surviving the calamitous trip back home.

"It isn't good," he said of the birds' chances. "Even if they were in shape ... They've got to get all the way back north."

He's confident some of them will survive the trip.

Robbins isn't ready to put a number on the percentage to survive, but he fears the stress will just be too much for most of the birds.