LINCOLN, Neb. (AP) — Environmental experts in Nebraska say transmission lines to power pumping stations for the planned Keystone XL pipeline would threaten endangered whooping cranes.

Representatives from environmental groups including the Sierra Club and Bold Nebraska submitted written testimony on Monday to the Nebraska Public Service Commission.

They say they object to the $8 billion pipeline’s impact on natural resources. The commission regulates the pipeline route through Nebraska.

Bird expert Paul Johnsgard says the preferred route of the pipeline would mean nearly 70 miles (110 kilometers) of new power lines in the state would pass through migration areas where whooping cranes roost and feed. He says that increases the risk of bird deaths from collisions.

Pipeline developer TransCanada says it’ll review comments but that the route doesn’t cross critical habitat for whooping cranes.