Alaska Birding with PIB: Birding Anchorage to Denali 14 June 2019
The first time I saw an Arctic tern was on a bird outing at Cape May, New Jersey in May 2004. It was the only Arctic tern perched in a big flock of common terns. How to pick it out of the crowd? “Look for the tern with the short legs.”
Arctic, common and Forster’s terns are in the same genus so it’s a challenge to identify them, especially since we don’t get any practice with Arctic terns in Pittsburgh.
In Alaska, terns are simpler. There are only four species: Common tern is very rare. Caspian tern is the only one with a big carrot-red bill. Arctic terns are everywhere and Aleutian terns look different.
Famous for their long distance Arctic to Antarctic migration, Arctic terns (Sterna paradisaea) are pale gray and white with uniformly silver gray upper wings, small round heads, short dark red bills, and short red legs. In the breeding season they have very long white tail streamers.
When they’re breeding Arctic terns are quite vocal. If you get too close to a nest they shout and dive bomb you. How close is too close? On the tundra where they nest alone, you may not know there’s a nest until you’re under attack.
Aleutian terns (Onychoprion aleuticus) are uncommon and local but easy to identify because they’re dark gray with white tails, white foreheads, black legs, black bills, and white edging on their wings. There’s no mistaking who they are when they’re standing.
You can see the Aleutians’ white foreheads in flight.
Even though it’s not a useful field mark in Alaska, Arctic terns are still the ones with the short legs.
(photos from Wikimedia Commons; click on the captions to see the originals)