- Appearance: in summer(left) black-capped head black eyes, orange beak tipped with black, pale grey back and belly; in winter(right) part of cap fades to white, beak, legs, wing’s edges become black, belly becomes white; long wings, forked tail
- No noticeable difference between males and females
- Length:12-15 inches (about 1 foot)
- Wingspan:30-32 inches (about 2.5 feet)
- Status:common, most widespread tern in North America
- Almost hunted to extinction during 1800s – feathers used for women’s fashion
- In the 1700s-1800s, tern eggs were also harvested for food
- Under 1918 Migratory Birds Act, common tern repopulated
- Common tern is threatened by habitat loss, competition from seagulls, water pollution, and climate change
- Almost hunted to extinction during 1800s – feathers used for women’s fashion
- Habitat
- Mostly live in marine habitats such as beaches, estuaries, and barrier islands
- During breeding season, may also forage in fresh- and saltwater marshes
- Spend a lot of time over open ocean, especially during migration and winter
- Found seasonally across North America, Mexico, and Caribbean Islands
- Also widespread across Eastern Hemisphere (Eurasia)
- Vulnerable to losing beach habitat to humans or being displaced by gulls and other birds that are relocating to a new habitat after theirs was lost
- Diet
- Small fish, crustaceans, squid, and insects
- Either catch fish from surface on the wing or plunge into water to get fish under water
- Forage in groups, often feeding on schools of fish at once
- Groups may have up to thousands of terns from different species
- Sometimes steal food from other terns and gulls
- Ability to drink midflight by dipping beak into fresh- or saltwater
- Special glands in beaks excrete salt from water
- Long, narrow wings allow for graceful midair maneuvers
- However, their short legs make them clumsy on land
- Migration
- All common terns are migratory
- In North America, the shortest possible migration path is about 12,000 miles
- Found on Long Island, Northeastern U.S., and Canada during breeding season
- Overwinter along Gulf Coast, in Mexico, and in Caribbean Islands
- In Eastern Hemisphere, breed across Europe and Asia and overwinter in Africa
- May migrate during the day or at night
- Average flight speed is 25-35 mph
- Nesting
- Nest on sandy beaches or rocky islands
- Choose mates with similar bill sizes -”assortative mating”
- Ground nesters – dig bowl-shaped depressions
- If their nest is threatened by rising water, common terns quickly raise their nest by stacking vegetation, shell pieces, and anything else they can find
- Average brood is 1-4 olive eggs with brown blotches, may have a second brood
- Adults aggressively defend nest- attack other birds, and if human gets too close they dive bomb and peck their heads or defecate on them
- Juveniles have brown-gray fish-scaled feathers, black cap, black and orange beak, orange legs, black along front edge of wings, dark tail
- Learn to fly after about 3-4 weeks
- During their first year, juveniles stay on wintering grounds during breeding season, making their first trip back when they are 2 years old
- Average lifespan is 10-12 years, but oldest common tern was about 35 years old