Common Tern

Sterna hirundo

(c) John Fuller
  • LARIDAE
  • Gulls, Terns, and Skimmers
  • Charadriiformes
  • Charrán común, Gaviotin común
  • Sterne pierregarin
Introduction
The Common Tern is the most widespread North American tern. This streamlined, elegant seabird is a familiar sight along the eastern seaboard, performing graceful aerials and plunging into the water from flight.
Fun Fact

The widespread killing of Common Terns, as well as herons and other waterbirds during the late 19th century, spurred the creation of the Audubon Society and other conservation organizations.

(c) Jim Fenton
Bird Sounds
© Lang Elliot, Nature Sound Studio
Vocalization

Long, harsh "keeeerrr."

Appearance Description
This medium-sized tern weighs about 4.2 ounces (120 grams), and measures about 12 inches in length with a wingspan of about 30 inches. Both sexes look alike—grayish-white with a black cap and wingtips, a long, deeply forked tail, red legs, and a red bill tipped with black. They are distinguishable from Forster's Terns by the dark carpal bar on non-breeding adults.
Range Map
Courtesy of Kenn Kaufman
Range Distribution
Common Terns breed from northwestern Canada southward to Montana, and eastward to Newfoundland and New Jersey, southward along the Atlantic Coast to Louisiana. They winter primarily in Argentina, Brazil, and other parts of South America, Africa, Asia, and Australia.
 
A legend for the range map to the right can be found here.
Habitat
Common Terns are found in a variety of fresh- and salt-water habitats, including estuaries, bays, lakes, and marshes. They nest on islands, marshes, and sometimes lake and ocean beaches.
Feeding
Common Terns feed primarily on small fish; they also eat invertebrates such as shrimp and other crustaceans, insects, marine worms, leeches, and small squid.
Reproduction
Common Terns breed in colonies, and nest on the ground; nests consist of a shallow scrape or depression, sometimes lined with grasses, seaweed, or shells. They usually lay up to 3 olive-buff eggs, marked with numerous dark brown blotches. Both sexes incubate the eggs and care for the young. Incubation lasts 3 to 4 weeks. The downy chicks are born able to walk, with their eyes open, but stay in the nesting colony until they begin to fly, at nearly 4 week of age.
Migration
All North American Common Tern populations are migratory. Terns conduct their high altitude migratory flights mainly at night; there are few records of daytime migration. Because most mortality probably occurs in winter, additional information is needed about existing conditions in the terns' winter territories.
  • 2,700,000
  • 430,000
  • 300,000 at large, managed colonies; 100,000 at large, unmanaged colonies; and 30,000 at small colonies – down from 100,000 40 years ago
  • 70 percent of the populations in smaller, unmanaged colonies have vanished in the last 40 years; however, trends for large, unmanaged colonies are unknown. Managed colonies along the Atlantic Coast and Great Lakes are stable or increasing.
  • severe population declines
Population Status Trends
Common Tern populations were devastated by egg and plume hunters over a century ago; protective legislation and intensive management have since led to rebounded populations, though not to historic levels. Recently, increased predation and other factors are reflected in the current Breeding Bird Survey (BBS) data, which show significant decreases in some populations, particularly in inland areas.  They are listed as endangered, threatened, or of special concern in many states.   
Conservation Issues
Tern wings, and even whole terns, were a common sight on ladies' hats in the late 1800s; intensive hunting for this purpose contributed to the species' demise. Though populations recovered with legislative protection, they began to decline again in the 1930s, as gulls took over many tern breeding areas. Pesticide-induced reproductive failure also contributed to major population declines during the 1960s, especially at freshwater sites.
 
Various conservation efforts have since benefited Common Terns, including better regulation of pollutants, management of landfills which feed competing gulls, protection of breeding sites against human disturbance and development, and removal of gulls from tern nesting areas. Although coastal tern populations increased during the 1980s and 1990s, maintaining these numbers requires ongoing management that is labor intensive and expensive.
 
Fortunately, Common Terns readily respond to management and habituate to researchers. They are among the most intensively researched birds, for studies including their behavior, dietary and breeding habits, ecology, anatomy, and toxicology. Information resulting from the banding of over one million Common Terns in North America has led to a better understanding of their migration, dispersal, demography, age-related biology, and causes of death.
What You Can Do
Never leave fishing lines, lures, or hooks on beaches; entanglement kills numerous terns each year.
 
Don't dump garbage or fishing bait which feeds competing gulls.
 
Don't disturb nesting tern colonies when hiking or landing boats; prevent dogs and children from disturbing them. When parents abandon the nest, eggs or chicks can overheat or become wet and chilled, often resulting in death.
 
Make environmentally-friendly seafood choices which encourage sustainable fisheries; this helps to protect the fish that Common Terns and many other seabirds  depend upon.
 
 
Protect the Boreal Forest Promote conservation of the Canadian boreal forest by supporting the Boreal Songbird Initiative that works to save Canadian boreal habitat for all birds, specifically by fighting inappropriate logging, mining, and drilling, and by promoting the designation of protected areas.

Conserve Wetlands Support wetlands conservation programs such as the Clean Water Act, North American Wetlands Conservation Act (NAWCA), and Farm Bill conservation programs such as the Wetlands Reserve Program (WRP), and “swampbuster” (the rule that restricts wetlands from being converted to agriculture). Encourage governments at all levels to enact and enforce wetlands protection and water quality laws and regulations.

Patrol Beaches Join beach watches to look for oiled birds or other signs of coastal pollution. Lobby with local, state, and federal officials to maintain wildlife-friendly beaches and clean coastal waters.

Support Waterbird Initiatives Support Audubon’s Project Puffin, which works at tern and seabird colonies in Maine, as well as Audubon Vermont’s work on Lake Champlain. Support nongovernmental organizations like STINASU, the Foundation for Nature Conservation in Suriname, that strive to protect waterbirds, including Common Terns, from habitat destruction and illegal killing.
More Information
Natural History References
Nisbet, Ian C. T. 2002. Common Tern (Sterna hirundo). In The Birds of North America, No. 618 (A. Poole and F. Gill, Eds.). The Birds of North America, Inc., Philadelphia, PA.
 
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, Inc., New York, 2000
 
Kaufman, Kenn. Lives of North American Birds. Houghton Mifflin Company, New York, 1996
Conservation Status References
Nisbet, Ian C. T. 2002. Common Tern (Sterna hirundo). In The Birds of North America, No. 618 (A. Poole and F. Gill, Eds.). The Birds of North America, Inc., Philadelphia, PA.
 
Sibley, David Allen. The Sibley Guide to Birds. Alfred A. Knopf, Inc., New York, 2000.
 
Kaufman, Kenn. Lives of North American Birds. Houghton Mifflin Company, New York, 1996.