MCNARY DAM – Every year during the summer months, the Columbia River is alive with millions of young salmon making their long journey to the Pacific Ocean. To reach their destination, the salmon must navigate through hundreds of miles of river, pass through the Columbia’s dams and locks, all the while evading ravenous predators.

Scientists are beginning to question whether too many young salmon are losing their lives to the growing flocks of American white pelicans living near the dams. In fact, scientists worry that the birds may have chosen habitats such as McNary Dam because of the easy fishing as the young salmon exit the dam’s by-pass channel.

“The pelicans are opportunistic and they’re looking for the best foraging conditions,” said Brett Tiller, a scientist for the Pacific Northwest National Laboratory.

Tiller and his team are working with the Army Corps of Engineers below McNary Dam to use new radio technology to observe the eating habits of the graceful white pelicans, who traditionally only prey on larger fish.

The cornerstone of the $175,000 study, under way since June, is a monitor not much larger than a Matchbox car that is affixed to the bird’s bill. Scientists will use the monitors to observe three aspects of pelican behavior: how much time the birds are spending near the fish detour at the bottom of the dam; how much feeding they do in this area; and how much fish the pelicans catch.

The $35 monitors transmit within only a quarter-mile area below the 18-story dam, exactly where the small salmon re-enter the Columbia. Because the American white pelican fishes while it swims, the monitors, encased in a gray plastic box, transmit how many times the pelican’s beak goes below the water, a sign the bird is fishing. It also will count the number of times the bird’s bill tips back quickly, which usually signals that a bird has caught a fish.

Scientists will use this information to estimate how many young salmon the flock of pelicans are eating, Tiller said.

So far, scientists have snared 15 birds in leg traps on the small islands below the dam where the birds rest. Scientists attached the small monitors onto the birds’ beaks using a medical adhesive. The monitor weighs just more than an once, scientists say, and does not impede the birds from their normal habits. The team has been lucky so far, Tiller said, because most monitors are staying in place for two weeks, plenty of time for a solid scientific sample. Scientists plan to trap another 35 birds before finishing in August.

In the past, researchers relied strictly on visual observation to trail the birds’ behaviors. That was time consuming. The radio technology allows information to be processed whenever the birds enter the area near the dam, Tiller said.

Pelicans first came to the Columbia River basin 20 years ago, Tiller said, but their population has increased in the past three years. In 2001, scientists estimated that 60 pelicans called McNary Dam home, while that number is nearly 100 now.

On any given day, each pelican will eat about 11 pounds worth of food. If they are eating young salmon, Tiller estimated each pelican could be eating up to 60 a day. While that may sound small compared to the estimated 125,000 to 500,000 young salmon that cross through the dam each day, Tiller points out that any lost salmon is lost savings for the Army Corps of Engineers , who have spent millions on protecting fish habitat in the Columbia River basin.

The team also may use the findings, which are due in January, to prescribe adjustments in how salmon are allowed downstream through the dams. Tiller hopes that the more salmon saved during the trip to the Pacific will only increase the chances that more adults will come back.

“Enhancing the return of adult fish, that is our goal,” he said.