MPR's Brent Wolfe has this Mainstreet report on the study of tundra swans. The Upper Mississippi River between Wabasha and La Crosse is a temporary home to as many as 15,000 tundra swans, as they stop off here each winter enroute from their breeding grounds along Alaska's north slope to their wintering grounds on the Chesapeake Bay.
Scientists know a fair amount about swan behavior at the breeding and wintering grounds, but they're just beginning to study where they spend their time on the river and what impact they have on the Upper Mississippi River Wildlife Refuge.
Transcripts
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BRENT WOLFE: On a recent evening, after the moon has set behind the Mississippi River bluffs, University of Minnesota graduate student Erik Thorson and his field assistant set off from Stoddard, Wisconsin, on a mission to catch tundra swans. Thorson perches in the front of a small canoe-like skiff with a flat stern. He's holding a big net on a pole and wearing a miner's light on his head. An assistant steers the boat with a small electric trolling motor.
Thorson gives hand signals about which direction to go as he listens for tundra swans. He seems to have a sixth sense about where the swans are and turns on the bright light strapped to his head. Two swans and a cygnet appear in the beam.
Thorson follows one bird, but it clearly knows something's coming. It paddles quickly with its head low to the water, kicking up a tiny wake. Thorson wrestles the bird into the boat and prepares to fit it with a radio collar. He wants to know if swans stay on one part of the river or whether they move around.
ERIK THORSON: So now, what we're going to do is process and band this bird. First of all, we're going to sex it and determine whether it's a male or female. We already know it's an adult because it's in full white plumage. And then we'll weigh it and then take five body measurements.
And then we'll put a Fish and Wildlife Service metal leg band on it and then also put a neck collar on with a transmitter attached. That'll be our last step. And then we'll release him back into the wild. And he can find his family again.
What I'm doing now is just tucking her head underneath her wing. She'll kind of go to sleep a little bit. And that way, it should be a little less resistant when we sex her. Female.
BRENT WOLFE: Thorson says after his initial two-year study on swan movement and population numbers, he wants to find out more about what they eat on the river.
ERIK THORSON: Swans are primarily aquatic foragers. Especially on the river here, we think that they're eating wild celery tubers and also arrowhead tubers.
BRENT WOLFE: Wildlife officials want to know how much swans are eating and if they're depleting food supplies for other bird species. Some hunters have suggested a season on the tundra swans could help control their numbers. But wildlife officials say that's unlikely because tundra swans look too much like endangered trumpeter swans that also use the river. Thorson says he's surprised some of the swans he's collared near Wabasha are already on the move.
ERIK THORSON: Two of those birds have moved quite a way south, probably 60 or 70 miles south in the Wisconsin islands. So it's very interesting to see movements down the pools. And also, we can see daily movement patterns of birds.
BRENT WOLFE: Birds like geese tend to stay in one area until it freezes over. The probing, measuring, and collaring of this swan is almost done.
ERIK THORSON: OK, putting the radio transmitter on, neck collar. And it's just held in place with two rivets.
BRENT WOLFE: Thorson lifts the swan out of the boat and floats it off onto the river. Instead of flying off in a great commotion, it paddles silently away into the darkness, until finally, the sleek white form is out of sight. Erik Thorson will soon understand more about what swans do on the river during their short stay each year. But he acknowledges scientists are a long way away from understanding how tundra swans and other migrating birds navigate thousands of miles, year after year. I'm Brent Wolfe, Minnesota Public Radio.