Arctic Tern Identification Guide

Key Field Marks

• Medium-sized tern, about 13-15 inches (33-39 cm) long including very long, thin tail streamers that extend past the folded wingtips at rest.
• Bill is entirely blood-red with no black tip (an important difference from the similar Common Tern).
• Legs are short and red — noticeably shorter than the legs of Common Tern, giving Arctic Tern a lower, more horizontal posture on the ground.
• Body plumage is pale gray above and below, with a neat black cap; underparts can look uniformly pale gray, sometimes with a faint darker gray wash on the breast in fresh breeding plumage.
• Wings appear translucent and evenly gray in flight, lacking the dark wedge on the outer primaries typically shown by Common Tern.

Behavior

• Graceful, buoyant flier; hovers over water before plunge-diving for small fish.
• Holds the record for the longest known migration of any animal, traveling from Arctic and subarctic breeding grounds to Antarctic waters and back each year — a round trip that can exceed 40,000 miles (64,000 km) annually.
• Nests colonially on open ground, and is famously aggressive in defending nests, often diving at and striking intruders (including people).

Separating from Similar Species

• Common Tern: bill typically shows a black tip (especially later in the season), legs are longer, and the outer primaries show a darker gray wedge; overall structure is slightly bulkier with shorter tail streamers.
• Forster's Tern: paler primaries that look silvery rather than dark, an orange bill with a black tip in breeding plumage, and a different, more contrasting winter head pattern with a black eye patch.
• Overall shorter legs, an all-red bill, and very long tail streamers are the quickest clues to Arctic Tern.

Habitat & Range

• Breeds on Arctic and subarctic coasts, islands, and tundra across the northernmost parts of North America, Europe, and Asia.
• Migrates enormous distances offshore to spend the nonbreeding season in the Southern Ocean near the edge of Antarctic pack ice, experiencing more daylight than any other animal over the course of a year.
• Away from breeding colonies, most often seen well offshore during migration.

Voice

• Sharp, high-pitched "kee-kee-kerr" and harsh "kip" calls, especially vocal and aggressive near breeding colonies.