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Least Tern (Interior Population)

Sternula antillarum

Fact Sheet


Least tern

Least tern

Photo by Wayne Hathaway for the Tern and Plover Conservation Partnership

The interior population of the least tern (interior least tern) is an endangered species.  Endangered species are animals and plants that are in danger of becoming extinct.  Threatened species are animals and plants that are likely to become endangered in the foreseeable future. Identifying, protecting, and restoring endangered and threatened species is the primary objective of the U.S. Fish and Wildlife Service’s endangered species program.


What is an interior least tern?


Least terns are the smallest members of the tern family. Terns are generally considered seabirds, but several species are also found along rivers, lakes, or other wetlands. The interior least tern is a migratory bird species, nesting along freshwater habitats of the Missouri and Mississippi rivers and their major tributaries and overwintering in the Caribbean and South America. Least terns primarily feed on small fish.


When was the interior least tern protected under the Endangered Species Act (ESA)?


On May 28, 1985, the U.S. Fish and Wildlife Service listed the population of least tern that occurred throughout the interior of the United States as an endangered species. 


Why was the interior least tern listed under the ESA?


Interior least terns historically nested along sand and gravel bars of the Lower Mississippi River and its major tributaries, including the Missouri, Red, Ohio, and Arkansas rivers. At the time of listing, the interior least tern was believed to have been eliminated from much of this summer nesting range by the construction of dams or other forms of river engineering, such as channelization that inundated and destroyed their nesting islands and bars and altered flow regimes. There were also a number of proposed water withdrawal projects on the southern plains that were potential threats to their habitats. In 1985, the population was estimated at fewer than 2,000 adults nesting in a few dozen scattered colonies along the Mississippi River and its tributaries.


How many interior least terns are there now?


Since being protected under the ESA, the numbers and distribution of interior least terns have steadily increased. They currently number approximately 18,000 birds.


Where are interior least terns found?


Interior least terns currently nest along more than 2,800 miles of river channels across the Great Plains and the Lower Mississippi Valley, with nesting colonies documented in Montana, North Dakota, South Dakota, Nebraska, Colorado, Iowa, Kansas, Missouri, Illinois, Indiana, Kentucky, New Mexico, Oklahoma, Arkansas, Tennessee, Texas, Louisiana and Mississippi.


Least tern chick and two eggs.

A least tern nest is a shallow depression in sand or gravel. The eggs and chicks are well camouflaged.

Photo by USFWS; Jane Ledwin

Where do interior least terns nest?


Interior least terns generally nest on the ground, in open areas away from trees, and on or near bodies of water that provide them with fish. Although they are primarily found along river channels, they will also nest on reservoirs, as well as sand and gravel mines, coal mines, and industrial sites where conditions are appropriate and occasionally on rooftops of buildings near bodies of water.


How does the Service determine if a species has recovered and no longer meets the definition of threatened or endangered under the ESA?


The Service periodically conducts a review of the status of all listed species, as required by the ESA, and considers a number of factors in determining if they have recovered. These factors include population size and distribution, the current and future status of the species, and threats to it. The Service conducted a thorough review of the interior least tern and found that the interior population of the species has recovered based on the increase in its abundance and distribution, the implementation of beneficial management practices across its range, and existing regulatory mechanisms that protect migratory birds.


What factors led to the recovery of the interior least tern?


Federal and state agencies, tribes, non-government organizations, and industry partners all contributed to the recovery of the interior least tern. Data sources and conservation partners include 19 FWS field offices in four regions, five divisions of the U.S. Army Corps of Engineers (Corps) and 13 districts, three U.S. Geological Survey science centers, 18 states, and multiple non-governmental organizations, including conservation organizations, industrial partners, and universities. More than 30 of these groups have been involved in interior least tern monitoring. 

Depending upon local conditions and needs, active management has included: monitoring, protection of nesting areas, improved water flow, dredge material placement, as well as vegetation and predator control. Many of these beneficial activities have become standard practices and are anticipated to continue following delisting.

The most notable partner aiding in the recovery of the least tern is the Corps, which coordinated the only range-wide monitoring event in 2005. This effort supported the growing population trends observed during the previous two decades through partial range monitoring. The Corps also funded, with the assistance of the Service, the development of a habitat-driven, range-wide population model for the species. This complex model, developed with the American Bird Conservancy, considers interior least tern status and population dynamics with and without continued management at local, regional, and range-wide scales across 30 years.

Designed to evaluate 55 scenarios, such as habitat degradation and loss or changes in management, the modeling demonstrates potential future impacts on observed tern population growth rates by subpopulation, population, or range. The analyses conclude that the interior least tern population is resilient to potential changes in habitat conditions across its large river network.

The Corps also has jurisdictional authority over much of the species’ range. The Corps’ Mississippi Valley, Southwest, and Northwest divisions all have made formal post-delisting monitoring and conservation commitments that encompass about 85 percent of tern breeding populations.

What is the process for delisting under the ESA?


To delist a plant or animal, the Service must first publish a proposed rule in the Federal Register explaining why the species no longer warrants protection under the ESA. Our proposed rule is based upon the best available scientific and commercial information, and includes a description of the current status of the species, the success of recovery actions, and a description of how the recover needs for the species have been met. Once the proposal is published, the public may comment. After the public comment period closes, the Service reviews and analyzes all comments received. It will then make a final decision in light of that information. If we find that delisting is appropriate, we will publish a final rule. The delisting will take effect 30 days after publication.

Will the interior least tern receive any protection if it is delisted?


If delisted, the interior least tern will continue to be protected under the Migratory Bird Treaty Act (MBTA), which protects the bird and its parts, nests, and eggs from “take” and trade. Federal permits are also required under the MBTA for certain actions like scientific collection and relocation.
Executive Order 13186 (Responsibilities of Federal Agencies to Protect Migratory Birds) requires all federal agencies to use their authorities and conduct their actions to promote the conservation of all migratory bird populations. Actions authorized by EO 13186 that may benefit the interior least tern include: avoiding and minimizing adverse impacts to migratory birds; habitat restoration and enhancement, and preventing pollution or detrimental alteration of migratory bird environments; designing habitat and population conservation principles, measures, and practices into agency plans and planning processes; and promoting research and information exchange, including inventorying and monitoring of migratory birds.
The interior least tern will also continue to be considered under other federal environmental statutes and regulations such as the National Environmental Policy Act and Clean Water Act, which contain provisions emphasizing the protection and restoration of ecosystem function and quality. State laws protective of native wildlife will continue to apply to the interior least tern.


Will the status of the interior least tern continue to be monitored if it is delisted?


Yes. The ESA requires the Service to implement a system in cooperation with the states to effectively monitor the status of a species for a minimum of five years after delisting to ensure that it remains stable. The Service is also issuing a draft post-delisting monitoring plan for public comment.


How can I comment on the proposed rule or provide additional information about the interior least tern?


You may submit comments or additional information using the following methods:

1) Electronically:
Go to the Federal eRulemaking Portal:http://www.regulations.gov. In the search box, enter FWS–R4–ES–2018–0082, which is the docket number for this rulemaking. Then, click on the Search button. On the resulting page, in the Search panel on the left side of the screen, under the Document Type heading, click on the Proposed Rules link to locate this document. You may submit a comment by clicking on “Comment Now!”

 (2) By hard copy:
Submit by U.S. mail or hand-delivery to:
Public Comments Processing
Attn: FWS–R4–ES–2018-0082
U.S. Fish and Wildlife Service
MS: BPHC; 5275 Leesburg Pike,
Falls Church, VA 22041–3803.

We request that you send comments only by the methods described above. We will post all comments on http://www.regulations.gov. This generally means that we will post any personal information you provide us in your comments.

How can I learn more about the interior least tern and the proposed rule to delist?


The proposed rule to delist the Interior least tern and supporting documents are available on http://www.regulations.gov. In the Search box, enter FWS–R4–ES–2018-0082, which is the docket number for this rulemaking.





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