Abstract
The interior population of the least tern, a Midwestern bird whose historic abundance impressed explorers Lewis and Clark on their westward explorations, and three subspecies of beach mice found along the windswept barrier island sand dunes of the Gulf Coast have been added to the U.S. list of endangered and threatened species.
The actions, announced recently by the Interior Department's U.S. Fish and Wildlife Service, expanded the list of imperiled species to 854, of which 356 species are found in this country and 498 are found only in foreign countries. One of these newly-added species - the small, secretive Perdido Key beach mouse - is considered the nation's most critically endangered small mammal, with an estimated population of only 26 individual mice.
The interior least tern joins its relative, the California least tern, as a species receiving the protections of the Federal Endangered Species Act. (A third variety of least tern, the eastern or coastal least tern, found along the Atlantic and Gulf Coasts of the United States, is not an endangered species.)
This tern, a small bird with the black crown, forked tail, and graceful, buoyant flight pattern characteristic of the species, was once a common resident of the great river systems of the central United States. The bird historically bred along portions of the Colorado (Texas/Oklahoma), Red, Arkansas, Missouri, Ohio, and Mississippi rivers.
Lewis and Clark frequently observed the least tern along the length of the Missouri River and near the mouth of the Platte River. Historical data for the bird are poor, however, and estimates of original numbers are generally not available, although records indicate that it once bred over a much larger area and in a far greater number of colonies than it does today.
An estimated 1,400 to 1,800 interior least terns are believed to exist within the bird's historic breeding range, which includes Arkansas, Colorado, Iowa, Illinois, Indiana, Kansas, Kentucky, Missouri, Montana, Nebraska, New Mexico, North Dakota, Oklahoma, and Tennessee and inland portions of Louisiana, Mississippi and Texas. In many of these states, however, the least tern is virtually absent; in Louisiana, for instance, where it was a common breeding bird, it is now absent, as it is in Mississippi, and only 30 terns have been counted in Arkansas and Illinois, respectively.
The least tern's decline has been attributed to the flooding and destruction of its nesting islands by channelization projects and reservoir construction along the Mississippi River and many of its tributaries. On many of the remaining nesting islands, alteration of river flows has caused unfavorable growth of trees and other vegetation, curtailing use of these sites by nesting...