Riseofthe Interior Least Tern

The sight of dozens, then hundreds, of Least Terns rising from a mid-river sand bar is becoming more common along major river systems throughout the United States. It's a welcome sign of recovery for this endangered subspecies.

The Interior Least Tern, once considered rare, may soon be taken off the Endangered Species list, thanks to a partnership of ABC, the U.S. Army Corps of Engineers, and the U.S. Fish and Wildlife Service (FWS).

The success is in part due to management techniques that keep predators off nesting sandbars on the Lower Mississippi River. In a recent visit, ABC's Casey Lott called one site “least tern paradise” as he watched more than 500 of the birds circle and swoop.

“Not bad for a species many people thought was rare when it was listed as endangered in 1985,” he said.

Listing the Interior Least Tern

In the mid-1980s, little was known about river-nesting Least Terns outside of the northern Great Plains, where battles were raging about water management on the Platte and Upper Missouri rivers. These battles led to an endangered listing for “Interior Least Terns,” defined as any Least Tern nesting more than 50 miles from the Gulf of Mexico.

When it came to the Lower Mississippi, the partners decided to try a different approach.

Anatomy of the Tern Turnaround

FWS and the Army Corps used a little-known part of the Endangered Species Act, Section 7(a)(1), to write a conservation management plan that would make it easier for the Corps to do their job of keeping waterways navigable—without impacting high-priority species such as the tern.

FWS wanted the endangered birds protected. The Corps wanted to keep barge traffic moving. In the end, the solution was simple: an adjustment of the dikes used along the river to control water flows.

By “notching” the dikes, the Corps ensured that water flowed around both sides of the sandbars where terns nest. In this way, they created backchannels in the river that separated the nesting sandbars from the shore—keeping predators like cats and raccoons at bay.

World's Best Habitat for ILT

Lott says that habitat conditions for the Interior Least Tern on the Lower Mississippi River are better than anywhere else in the world, including coastal beaches.

He's encouraged that this success story may inspire other federal agencies to work together in innovative ways to recover listed species.

“It might even serve as a model for keeping species off the Endangered Species list in the first place,” he says.

De-listing the Tern

A final bit of good news: After ABC completed the first comprehensive population survey of Interior Least Tern in 2006, it was revealed that tern populations had reached or exceeded recovery plan goals under the Endangered Species Act in most of the key river systems where this subspecies is found.

That could portend a rare and welcome “de-listing” of the species in the near future.