The arctic tern, or Sterna paradisaea, is a medium-size seabird with a length of about 13-15 inches (33-39 cm), a wingspan of 26-30 inches (76-85 cm), and a weight of approximately 3.0-4.5 ounces (86-127 g). In appearance, the arctic tern has plumage that is mainly gray and white, along with a bright orange beak, a black head and a whitish tail. Distinctively, it has webbed feet and short, orange legs. Males and females resemble each other in appearance.
As might be expected, the habitat of the arctic tern is primarily in the northern latitudes where its breeding grounds are located. These arctic birds nest on the ground in close proximity to shorelines, marshes and tundra lakes. They can be found throughout the Scandinavian and Baltic coasts, in Siberia and along the shores of Greenland and Iceland. In addition, they nest in Britain, Ireland and Canada, as well as in the United States, where they can be found on the East Coast as far south as Massachusetts.
The breeding cycle of the arctic tern has caused it to become famous in the scientific community for its migration. During the northern summer, it can be found dispersed throughout its breeding grounds. After the breeding season is over, it begins the longest regular migration of any known animal as it flies to Antarctica for the southern summer. This is a round-trip journey of some 24,000 miles (38,000 km) when measured point-to-point from the Arctic to the Antarctic. These arctic birds are exposed to more daylight than any other creature on the planet since they are in both the Northern and Southern hemispheres during the periods when the days are the longest.
An arctic tern living 30 years, which many do, will have traveled the equivalent of three round-trip journeys to the moon during the course of its life. Perhaps as a consequence of the time spent migrating, the arctic tern has learned to perform most all of its life tasks in the air. Depending on their mating cycles, the birds land only once every one to three years.
Arctic terns mate for life and have elaborate courtship rituals. The mates must both agree on the site for their nest. As one of the more aggressive terns, both sexes defend the nest and their young. Both adults and the young are carnivorous, with their diets consisting mostly of small fish, crustaceans, krill and insects.