Story last updated at 9:23 PM on Wednesday, August 20, 2008

SandHill Cranes

Researcher tracks their migration

By Michael Armstrong
Staff writer

Judging by a large turnout last Friday for a talk by sandhill crane researcher Gary Ivey at the Alaska Islands and Ocean Visitor Center, Homer loves its sandhill cranes. The big gangly, dancing and squawking birds claim followers from Diamond Ridge to East End Road. Many homes with large, open fields have a family or two of cranes.


 

Photo provided

Caroline Herziger holds a captured sandhill crane that has been tagged for Gary Ivey's satellite telemetry study.

Ivey, a retired U.S. Fish and Wildlife Service biologist from Bend, Ore., and the western crane conservation manager for the International Crane Foundation, has been in town this summer working on a research project on the migration of sandhill cranes in the Pacific Flyway. Homer crane researchers Ed Bailey and Nina Faust, founders of the Kachemak Crane Watch, helped fund Ivey's project.

His talk last week gave an overview of sandhill crane biology and the purpose of his research. North America has six subspecies of sandhill cranes: greater, lesser, Canadian, Florida, Mississippi and Cuban. Two subspecies, the greater and lesser sandhill cranes, migrate on the Pacific coast, with the lesser sandhill crane, grus canadensis canadensis, being the species seen in the Homer area. Population surveys done by Kachemak Crane Watch estimate about 200 lesser sandhill cranes in Homer, Bailey said. Lesser sandhill cranes are about 3-3.5 feet tall and weigh 6-7 pounds, with greater sandhills 4-4.5 feet tall and weighing 10-14 pounds.

Lesser sandhill cranes migrate from their winter homes in the central California valley, fly east of the Cascade Mountains and through British Columbia and Southeast Alaska to breeding grounds in Alaska including Kachemak Bay. The males, known as roans, and the females, known as mares, pair up and hatch from one to two eggs. Sandhill chicks are known as colts.

Sandhill cranes mate for life like people, Ivey said.

"They divorce sometimes," he said.

Younger cranes occasionally switch partners, and there have been cases of pairs breaking up, mating with other partners, and then getting back together, Ivey said.

Like humans, sandhill cranes also can live long lives. Cranes in captivity have lived up to 84 years, and wild cranes have been documented to live 40 years. Chick survival is low. Ravens and crows eat eggs.

"Just about everything out there eats young cranes," Ivey said.

The adult survival rate is high, with most cranes dying from predators like coyotes and eagles. Cranes also die in collisions with powerlines and are legally hunted in Alaska.

"Eagles are probably the biggest overall predators," Ivey said.

Bailey a critic of human feeding of bald eagles such as that by Homer's Eagle Lady, Jean Keene said he's documented many killings of cranes by bald eagles.

Cranes also prey on other birds, particularly red winged black birds. On winter grounds, sandhill cranes can be spotted by looking for black birds harassing cranes, Ivey said. Sandhill cranes eat voles, crayfish, earthworms and grains like corn.

"They're really flexible and opportunistic," Ivey said.

Sandhill cranes entertain bird lovers with their leaping, wing flapping and dancing not all of it for mating. Sometimes their antics have to do with staking out territory.

"Cranes get very angry at people sometimes," Ivey said. "When they're throwing sticks, it's a big insult."

Roans tend to be larger than mares, but the best way to distinguish the sexes is by their unison call. When a pair of cranes make a call together, the roan raises his beak straight up while the mare raises her beak at a 45-degree angle to the ground.

On winter grounds, greater sandhill cranes tend to stay within a .66-square-mile area, while lesser sandhills wander in a larger area of 7.8-square miles.

Why they do that is one of the purposes of Ivey's satellite and radio-tracking study. Scientists have a good understanding of general flock behavior.

"We know what the flocks are doing," Ivey said. "We don't know what the individuals are doing."

Ivey has captured and put tracking devices on 10 Homer area sandhill cranes this year. The cranes carry both a satellite transmitter and a VHF radio transmitter. Ivey showed a slide of where the tagged cranes fly around Kachemak Bay. Most of the sandhill cranes tend to cluster around East End Road, with some flying out to Caribou Lake or to Anchor Point.

"They're moving around quite a bit," Ivey said.

Some at the talk last week expressed concerns about the extra weight on the cranes. The transmitters are attached to each leg of a crane and add about 1.5 ounces of weight to the bird. Cranes also get marked with a numbered band. Tagged cranes adjust to the transmitters, he said. Eventually the transmitters will fall off or so Ivey hoped, he said.

"There's no other good way to get this information," Ivey said.

Information about where sandhill cranes go can be helpful in managing crane habitat, he said.

"The biggest threat a huge threat is loss of habitat," he said.

A Web site showing the movement of the sandhill cranes tagged in Ivey's study will be up within a few weeks. Visit www.cranewatch.org for a link to that site. For information on the International Crane Foundation, visit www.savingcranes.org.

Michael Armstrong can be reached at michael.armstrong@homernews.com.

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