Pelican Feeding Habits Monitored at McNary Damby Anna King, Herald staff writer
Tri-City Herald, July 18, 2003
Some of the pelicans that feast on tiny salmon below McNary Dam are getting high-tech nose jobs this summer.
Researchers with the Pacific Northwest National Laboratory and Army Corps of Engineers are using special technology that was developed for the military as they try to find out how many juvenile salmon are being eaten by the flocks of American white pelicans that hang out below the dam.
"McNary Dam seems to have more (pelicans) around ... than other dams, so it was the first site picked," said Brett Tiller, the lead research scientist on the study for PNNL.
Ultimately, the researchers will be looking for ways the Corps can reduce the number of young salmon that pelicans take below the dam, perhaps through techniques such as controlling water flows.
This year, as many as 100 pelicans have been seen at once below the dam, Tiller said. One pelican can gobble down 30 to 60 young salmon a day, he said.
To determine how many fish are being eaten at McNary, the scientists are tagging pelicans with bright markers on their wings and special radio devices glued to their bills.
The radios are placed inside a candy bar-sized plastic box that is then super-glued to a pelican's bill. It transmits data back to the scientists for two to three weeks before it harmlessly falls off, Tiller said.
"If we are even able to get two weeks of data off these tags while the birds are up here, we think we have some good data," he said.
Fifteen birds have been tagged so far, and scientists hope to study as many as 50 before the summer is over.
Two sensors in the tag device record the pelicans' feeding. When a bird dips its bill into the water, the sensor registers a "dip," Tiller said. Then when the bird tips its head back beyond 60 degrees to swallow a fish, it records a "successful dip," or feeding.
Bright tags also are affixed to the birds' wings through their skin, similar to an ear tag on a cow. Researchers nearby use binoculars to look at the numbered tags to confirm which birds are at the dam, how often and if they've been seen elsewhere in the area.
Before the study, scientists could only count how many birds were at the dam at a specific time, Tiller said. And they didn't know where the birds came from. Now if tagged pelicans are spotted elsewhere on the river, researchers can chart their movements.
"We want to see if there is a group of pelicans just living here or if they are always changing," said Ian Welch, a PNNL biologist.
The birds, which are listed by the state as endangered, may like McNary Dam because it's close to their breeding colony site near the mouth of the Snake River.
Tiller said the pelicans like to prowl the water below the dam, where they can find young salmon that are disoriented after going through the dam turbines or fish bypass system. When the birds have eaten their fill, they sit on little shelves of land alongside the river.
That's where the scientists dig a hole and camouflage a specially designed leg-hold trap. When a bird steps into the padded trap, it holds the pelican by the first digit of its middle toe until researchers arrive.
The trapping, radio devices and tags don't hurt or distress the birds, Tiller said, and they are usually calm while being handled.
Tiller studied three captive pelicans last year in Salt Lake City to make sure the devices and tags wouldn't affect their feeding, social or breeding behaviors.
The study will continue until mid-August, he said.
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