A North Dakota wind farm may have to monitor the area for whooping cranes for years to come, even though the endangered big birds haven't been spotted since the facility began operating in 2010, federal regulators said.
The Basin Electric Power Cooperative employs biologists to watch for whooping cranes at the facility south of Minot every spring and fall when the tallest birds in America follow their usual migration route between Canada and Texas.
The Bismarck-based company is required to shut down its giant turbines if the birds come within a mile of the wind farm, according to the terms of a $250 million dollar loan from the U.S. Department of Agriculture's Rural Utilities Service. The cranes are federally protected and number only a few hundred in the wild.
About 80 wind turbines, each with three 123-foot-long blades attached to a tower roughly as high as a football field is long, occupy some 30,000 acres along a stretch of about six miles along both sides of U.S. Highway 83.
"If we see a whooping crane, we'll start shutting down the towers as fast as we can," said Daryl Hill, a Basin spokesman. "But we've never had a sighting at all."
Terry Ellsworth, a U.S. Fish and Wildlife Service biologist in Bismarck, said all wind farms must monitor for the birds during the first three years of operation and that Basin's three-year requirement at the North Dakota facility is due to end after fall migration this year. But that requirement could be extended.
"We're still learning," Ellsworth said Monday. "We'll determine if future monitoring is needed but no decision has been made yet."
Ellsworth said more than a dozen whooping crane sightings are confirmed annually in North Dakota during migration. Another Basin wind farm project near Chamberlain, S.D., turbines had to be shut down this spring after a pair of whooping cranes was detected, Hill said.
Three other wind farms near Wilton in north-central North Dakota funded by federal loans also are required to have private biologists on site during migration, Ellsworth said. Basin's $363 million, 37,000-acre wind farm in southeast South Dakota also must provide observers to scan the skies during whooping crane migration.
Hill would not disclose how much it costs to hire biologists to watch for the cranes. At least one observer has been at the North Dakota facility every day during spring and fall migration over the past three years. In South Dakota, two observers are on site daily during migration, he said.
Other employees at the wind farm also know how to spot the whooping cranes and can alert Basin's dispatch center to shut down the turbines if one is seen, Hill said.
The birds are about 5 feet tall and have a wingspan of about 7 feet. They are white with black wing tips. In flight they extend their long necks straight forward, and their legs extend out behind them. They usually fly alone or in small groups, sometimes with sandhill cranes.