The Center for Biological Diversity and Maricopa Audubon say they intend to sue the U.S. Fish and Wildlife Service and the Bureau of Land Management over grazing near the Gila River in eastern Arizona.

The center says the practice harms endangered birds.

The Gila River is home to the Southwestern Willow Flycatcher and Yellow-billed Cuckoo.

In the past, the Fish and Wildlife Service has issued opinions that say grazing along the Gila River won’t harm the birds, and the BLM has relied on those opinions to make land management decisions.

But conservationists say those opinions were flawed, and that grazing policy has been too lax.

They also point out that agency scientists have at times expressed concern over damage by cattle in the riparian corridor.