If whooping crane is sighted, it's time for a coffee break

As workers dig trenches for a new North Dakota oil pipeline named after a bird called the sandpiper, they'll need to look out for another avian visitor — the whooping crane.

If they see any, workers must take a break until the endangered cranes fly out of sight.

Pipeline company Enbridge Energy promised regulators this week that it would take such steps while building its planned $2.6 billion Sandpiper pipeline to transport crude oil from the Bakken region to a Superior, Wis., oil terminal.

In a regulatory filing in North Dakota this week, Enbridge said the western portion of the planned pipeline lies within the Central Flyway, a bird migration route across the United States and Canadian plains that is used by whooping cranes. Large wetlands adjacent to the pipeline route are possible crane roosting areas during migration, Enbridge said in the filing.

Over the years, federal wildlife officials in North Dakota have required crane-related work stoppages for dozens, if not hundreds, of construction projects along the flyway, from wind farms to highways, said Jeff Towner, the state field supervisor for the U.S. Fish and Wildlife Service. But the temporary work shutdowns are rare, he said.

"It does happen once in a while," said Towner, who added that no violations of the rule have been reported. "If they see a whooping crane, and it can be overhead or on the ground, we ask them to please stop and call us."

The crane migrations between the Texas coast and Canada occur in spring and fall. Enbridge said that if ­contractors or inspectors spot a crane, "construction activities within 1 mile of the sighting will be stopped until the birds have left the area."

Whooping cranes have recovered from a low of 21 birds in the wild in the 1940s to nearly 600 wild and captive birds in 2010-2011, according to the International Crane Foundation, which is based in Baraboo, Wis. The group's website says the recovery is "one of conservation's most inspiring success stories." Last month, two groups of cranes were released in Wisconsin, and were being led by ultralight planes to Florida.

The 600-mile Sandpiper line, which also is under ­regulatory review in Minnesota, is expected to employ 3,000 construction workers, split about evenly between the two states, with work beginning in late 2014 and finishing in 2016.

When completed, the 225,000-barrel-per-day pipeline will have the capacity to carry away roughly 20 percent of the Bakken region's crude oil production. The segment between Enbridge's Clearbrook, Minn., and Superior terminals will have greater capacity, and more details about the preferred route are expected to be filed with Minnesota regulators this month.

David Shaffer • 612-673-7090 Twitter: @ShafferStrib