Tracking sandhill cranes

Biologists are tagging cranes to learn more about this bird, which moves through Alaska by the thousands

Posted: Monday, May 14, 2001

PALMER - You could hear the sandhill cranes coming.

Wave upon wave of calls chittered across the valley with tremendous urgency, getting louder with each second. As the sound filled the sky over a Matanuska Valley potato farm, biologist Mike Petrula sat up in his hiding spot under a spruce tree and scanned the field with binoculars for landing cranes.

"It sounds almost prehistoric," he muttered.

Thousands of cranes arrive through upper Cook Inlet during the spring migration from California to Alaska, with some stopping in Southeast Alaska. Some nest by the inlet for summer, others move west to Bristol Bay and beyond. And in the fall they return south in high, jabbering flights. But many details - where they go, where they eat - remain unknown.

To find out more, Petrula and other biologists from the Statewide Waterfowl Program in the Alaska Department of Fish and Game are capturing a dozen birds this season and tracking them with satellite transmitters during the coming year.

After an hour of waiting in the potato field, no cranes had approached the cracked corn spread on the ground to lure adult birds within reach of a rocket-propelled seine net. Now that was about to change.

The noisy flock suddenly appeared above the trees, silhouetted against the snowy skyline of nearby peaks. Their high-pitched racket was more like a discordant jumble of human voices than bird calls. The cranes circled in unison, then cupped their broad wings and crooked their long necks forward and descended into the field. More cranes followed and within minutes, a few hundred birds milled among shriveled potatoes and old stalks.

"I'm getting excited now," Petrula whispered.

 

For a time the cranes - 3 feet tall, with long black legs, red foreheads and gray plumage - flirted with the bait, pecking the ground and bickering among themselves. Finally, a row slowly walked into the corn. Petrula radioed his co-workers hiding in brush to detonate the rockets, which boomed, yanking up the 60-foot by 30-foot net. As Petrula and five other biologists dashed forward, hundreds of cranes exploded into the air, crying and squawking.

Nine cranes were trapped.

More than half a million cranes return to the North each April and May, nesting in marshes and wet tundra from northern Canada through Siberia. Several hundred stop for spring snacks along the Anchorage Coastal Wildlife Refuge. Last year, field biologists identified nine crane nesting areas a few hundred feet from the bluff.

But a small, apparently distinct group summers in upper Cook Inlet, the Kenai Peninsula, the Alaska Peninsula and Bristol Bay. This lesser-known bunch follows the Pacific Flyway - the Copper River Delta, Southeast Alaska, British Columbia, Washington and Oregon - to wintering grounds in California's central valley.

As part of on-going research that began last July with transmitters attached to six birds, the biologists plan to clamp more transmitters on 12 more birds. But first they have to catch them.

In the Matanuska potato field, six state biologists scattered to individual cranes pinned by the net. The men lifted the mesh, untangling talons and beaks and wings, then guided the birds out so they could be wrapped up for measurements or freed.

In a few minutes, the biologists had released three of the smaller birds. The rest were wrapped in bags and hoods, legs secured with Velcro straps, or held by biologists.

The bird cradled by Dan Rosenberg held its head up, glaring with yellow eyes. It pulled at his shirt with a talon, then shot its bill toward his face. Finally Rosenberg let it clamp down on his gloved thumb, which seemed to calm the bird.

In turn, a pair of biologists quickly measured bill length, leg bone, the middle toe and nail, and a portion of the wing. Alaska's biggest game birds, these cranes weighed 8.5 to 9 pounds - their black flexible bills extending 4 inches, middle toes reaching more than 3 inches to end in sharp black nails. Blood was taken from the under the wing to find out sex and genetic heritage. Biologists clamped leg bands on four birds, so they could be identified if sighted, captured or shot in the future.

And three birds each received an 8.5-ounce satellite transmitter - a small yellow cylinder placed around a leg. For the next year, the $3,000 units will send out a pulse every 60 seconds, giving fixes to one of four polar satellites. Their progress across Alaska and North America will be posted on the Web.

The birds were released one at a time. One took two big strides as it extended its wings and sprang into the air. It pumped hard, rose fast, banked sideways on the gusting wind, then circled above the trees and soared from sight, heading toward the cry of the flock.



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