Not every bird is a snowbird

Some stay in the North far beyond what's good for them

Posted: Tuesday, December 21, 2004

FAIRBANKS - A sharp-shinned hawk loitering at a bird feeder, mallards lounging in a section of the Chena River that never freezes and robins flying around Fairbanks.

There are always a few birds that remain in the Far North each winter instead of heading south.

"We've still got a junco coming to the feeder here," said bird biologist Susan Sharbaugh at the Alaska Bird Observatory. "It's kind of cool."

No pun intended, of course, since most of the birds that stay behind end up freezing or starving to death.

Sharbaugh said more migrant birds may be hanging around Fairbanks in the winters because temperatures have been warmer than normal.

"Birds migrate to change their environmental conditions and go some place more favorable," she said. "If they're in a place where the environment is changing in a way so they can meet their nutritional demands, why leave?"

While there are about two dozen resident bird species in the Interior, 50 species have been recorded in Fairbanks over the past 44 years in the Christmas Bird Count, said count coordinator Gail Mayo.

This year's Christmas count is scheduled for Jan. 2 and Mayo expects a few oddballs to be recorded.

"We always have a few birds in that category," she said of migrants that don't migrate.

Last year it was a brown creeper. In 1994 it was a rustic bunting. The year before that it was a rosie finch. There was an American coot on the cooling ponds at Fort Wainwright more than a decade ago. The 1976 count included a Savanah sparrow.

Hawk owls, and golden- and white-crowned sparrows also have been reported in the Christmas count. Robins show up almost every year and have been seen late into February, leading experts to wonder whether they can actually make it through the winter.

"How they survive the cold, I don't know," said Nancy DeWitt, executive director at the Alaska Bird Observatory.

Whether birds simply choose not to migrate or don't leave because they can't is unknown. There are several theories as to why a bird would remain in a place like Fairbanks rather than fly south. It could be that they were injured and couldn't leave when they were supposed to and now it's too late.

"It's all speculation," said biologist John Wright at the Alaska Department of Fish and Game, who specializes in waterfowl. "I think a lot of the unusual birds we see in October or November and think, 'That guy should have migrated,' there is a physical reason why they're not leaving."

Another possibility is that the birds that stay don't put on enough fat to make the trip south, said Sharbaugh, who recalled a varied thrush hanging out by the air ducts at the Rasmussen Building on the University of Alaska Fairbanks several years ago.

"Part of being able to leave is getting into a physiological condition," she said. "There may be a threshold of fat they need to migrate that they haven't hit yet."

There may also be a specific window that birds migrate in. If they miss that window for some reason, the urge to migrate may disappear, said Sharbaugh.

Birds migrate out of necessity, not by choice, said Wright, who had a robin eating out of a crab apple tree in his yard a month ago.

"It's costly to migrate," he said. "It's a tradeoff between getting picked off by a raptor or a fox to trying to keep warm in a cold, dark place, which is what a lot of us do."



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