Interior Least Tern and Piping Plover

By Greg Pavelka
U.S. Army Corps of Engineers

In 1986, the interior least tern and the Northern Great Plains population of piping plovers were respectively listed as endangered and threatened by U.S. Fish & Wildlife Service.  Both these shorebirds nest on Missouri River sandbars below dams operated by the U.S. Army Corps of Engineers (Corps) and on reservoir shorelines.

As part of a biological opinion by U.S. Fish & Wildlife Service, the Corps annually conducts adult census and productivity surveys throughout the nesting season to determine population trends, nesting success and chick success for the two species.

Surveys are conducted along 1,000 miles of river and reservoir shoreline from Fort Peck Lake in eastern Montana to Ponca State Park in northeastern Nebraska.

Permanent and seasonal Corps employees at project offices along the Missouri River do these surveys.

The surveys begin in late April as piping plovers arrive from wintering grounds along the South Atlantic coast, Gulf Coast and shores of Caribbean islands. Least terns begin arriving from wintering grounds along the shores of Central and South America about a month after the plovers.

After the birds arrive crews track them weekly through egg laying, egg hatching, chick rearing and chick fledging (when the birds are able to fly).

Generally, the last of the fledglings and adults of both species leave for wintering grounds by mid to late August. Before then, an adult census is conducted the last two weeks in June. By that time the two species have settled down on nesting grounds and movement up and down the river is limited.

Tracking least terns and piping plovers is a high-tech operation. Crews carry a global positioning system (GPS) and data logger to survey sandbars and shoreline.

Finding nests isn’t easy as the nest bowl is just a scrape in the sand and the eggs of both species are camouflaged to blend into the sand.

When a nest is found, crews record the location with GPS and document species, number of eggs, egg incubation stage and nest fate. In the office the data is downloaded via computer into the Corps’ Threatened & Endangered Species Data Management System (DMS).

DMS is an Internet-based data depository. Once the data is in DMS, it undergoes a quality check and after approval, is available to users in a series of reports.

Users include the Corps, U.S. Fish & Wildlife Service and state game and fish departments. Reports include nest status, nest fate, adult census and chick productivity.

Throughout the nesting season the Corps’ Threatened & Endangered Species Section closely coordinates bird monitoring with the Corps’ Water Management Division.

The Water Management Division determines water releases from dams to meet project purposes such as flood control, hydropower generation, irrigation, fish and wildlife values and navigation.

Nests determined to be at risk from low sandbar elevation or rising lake levels are red-flagged by survey crews and special attention is given these nests and subsequently to the chicks if the eggs hatch.

Actions taken to protect at-risk nests and chicks include delaying water increases out of the dams until after the eggs have hatched or the chicks have fledged, to raising up nests and moving nests and chicks to higher locations.

This year saw record number of piping plovers and least terns on the Missouri River. The 1,764 adult piping plovers represent an 11 percent increase over 2004 and the 904 least terns represent a 25 percent increase over the number adult terns counted in 2004.

Productivity goals as set by the U.S. Fish & Wildlife Service in the biological opinion were also met for both species.

Data collected this year will continue to be analyzed for ways to improve bird survivability. DMS will also undergo a major overhaul as the Corps looks to improve data collection and analysis measures.