US Fish & Wildlife Service


Date of this Version



Shuford, W. D. 1999. Status assessment and conservation plan for the black tern (Chlidonias niger surinamensis) in North America. U.S. Department of Interior, Fish and Wildlife Service, Denver, CO.


U. S. government work.


The Black Tern (Chlidonias niger surinamensis) has been a species of concern in North America because of continent wide population declines, particularly since the 1960s. Currently the species is listed as Threatened or Endangered in 6 states and is considered of conservation concern in 18 other states and provinces. Breeding Bird Survey data indicate that Black Terns declined significantly survey-wide at an average rate of 3.1 % annually (61.1 % overall) from 1966 to 1996. Also during this period, the Canadian population decreased significantly at an average annual rate of - 3.5% (-65.7% overall), whereas the U.S. population showed no significant trend. These declines largely reflect trends prior to 1980, and most trends were reversed in the 1990s. The North American population recently has leveled off or increased slightly. The species still occupies most of its former range, and the continent wide breeding population probably still numbers in the low to mid hundreds of thousands.

The main causes of population declines in North America appear to be habitat loss and degradation on the breeding grounds, although introduced species, human disturbance, and contaminants may be contributing factors. Since the 1950s, the freshwater emergent wetlands upon which the species depends for breeding have declined by 25%. Very little is known, however, about threats to the Black Tern during migration and winter, which account for 8 to 9 months of the species' annual cycle.

Recovery of Black Tern populations likely will require a combination of management efforts and policy initiatives to improve habitat conditions and nesting success. Conservation priorities are (1) refining monitoring techniques to better detect population trends and determine the causes of changes, (2) stemming the tide of wetland loss by forming partnerships to protect and restore wetlands from a landscape perspective, (3) managing habitat for Black Terns based on current knowledge while conducting further research to identify limiting factors and evaluate additional management techniques, and (4) educating the public about the value of wetlands and possible effects of their actions on Black Terns.