Arctic Tern Life History

Habitat

Habitat Shorelines

Arctic Terns breed in treeless areas with little to no ground cover, in open boreal forests, and on small islands and barrier beaches along the northern Atlantic Coast. They forage over streams, ponds, lakes, estuaries, and the open ocean. They tend to migrate offshore although some individuals may migrate overland. Arctic Terns winter on the edge of pack ice in Antarctica during the Southern Hemisphere summer.

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Food

Food Fish

Arctic Terns take small fish from the surface of the water or plunge-dive just below the surface. They eat a variety of small fish species generally less than 6 inches long including sandlances, sandeels, herring, cod, and smelt. They also grab insects from the air or the surface of the water. During migration, they frequently forage with groups of other seabirds following schools of predatory fish that drive smaller fish to the surface.

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Nesting

Nest Placement

Nest Ground

Arctic Terns place their nests on the ground generally near water in areas with rocky or sandy ground. Sometimes they place their nests on top of short grasses or mosses.

Nest Description

Males and females make a scrape on the ground in an existing hollow or on flat ground. While sitting in the nest, they may add material to the rim of the scrape, using anything within reach from grasses to pebbles.

Nesting Facts
Clutch Size:1-3 eggs
Number of Broods:1 brood
Egg Length:1.4-1.9 in (3.6-4.7 cm)
Egg Width:1.0-1.3 in (2.6-3.2 cm)
Incubation Period:21-23 days
Nestling Period:21-28 days
Egg Description:

Olive to buff with numerous small dark brown spots and blotches.

Condition at Hatching:

Covered in down with eyes open. Hatchlings are able to walk, but stay in nest.

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Behavior

Behavior Aerial Dive (water)

Arctic Terns are buoyant and graceful fliers that frequently hover above feeding grounds and nesting colonies. They take small fish from the surface of the water or plunge to a depth of around 20 inches, rising out of the water with a shake and swallowing fish head first. They are often the target of food pirates such as jaegers and gulls that steal their catch. Arctic Terns are gregarious and breed in noisy colonies. Males fly low over breeding colonies with their fish-filled bill pointed downward to grab a female's attention. Interested females follow the crouching male in flight while the female passes over him with her body held straight. Courting continues on the ground with the male tipping his head down and holding his wings down and out from the body while the female stands nearby with her head pointed upward. The male starts offering food to the female, eventually feeding her almost exclusively as the pair bond is cemented. Pairs form monogamous bonds for the breeding season. Adults vigorously defend their nest site. Intruding birds are first met with a "bent posture"; adults tip their heads down and hold their wings down and out. Intruders that continue to approach are met with a more aggressive posture with the bill pointed upward and wings held down and out. When posturing fails, adults attack the intruder, often wrestling and fencing with their bills both on the ground and in the air. If humans enter the breeding colony they often dive towards them, peck their heads, and defecate on them.

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Conservation

Conservation Low Concern

Arctic Terns are common, but their arctic tendencies make estimating population trends challenging. The North American Waterbird Conservation Plan lists Arctic Tern as a species of high conservation concern, whereas Partners in Flight rates it an 11 out of 20 on the Continental Concern Score, which means it is not on their Watch List and is a species of low conservation concern. Partners in Flight estimates the global population at 3 million breeding birds. In the late nineteenth century Arctic Terns as well as Common Terns were targeted for the feather trade, which caused populations to decline. Most populations recovered following the enactment of the Migratory Bird Treaty Act in 1918. Other potential threats to Arctic Terns include human disturbance at colonies, degradation of barrier beach and island nesting habitat, and reductions in fish stocks.

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Credits

Dunne, P. (2006). Pete Dunne's essential field guide companion. Houghton Mifflin Harcourt, New York, USA.

Ehrlich, P. R., D. S. Dobkin and D. Wheye (1988). The birder's handbook. A Field Guide to the natural history of North American birds, including all species that regularly breed north of Mexico. Simon and Schuster Inc., New York, USA.

Hatch, Jeremy J. 2002. Arctic Tern (Sterna paradisaea), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA. 

Lutmerding, J. A. and A. S. Love (2016). Longevity records of North American birds. Version 2016.1. Patuxent Wildlife Research Center, Bird Banding Laboratory, Laurel, MD, USA.

Partners in Flight (2017). Avian Conservation Assessment Database. 2017.

Sibley, D. A. 2014. The Sibley guide to birds, second edition. Alfred A. Knopf, New York, USA.

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