Interior Least Terns

(Sternula antillarum athalassos)

The Interior Least Tern is a state and federally protected endangered species. It is the smallest tern in North America. The Interior Least Tern is an energetic, swallow-like bird with a deeply forked tail and slender wings. They are graceful, agile flyers and are often observed hovering over bodies of water and diving to catch small fish.

Interior Least Terns are:

  • slightly smaller than a robin
  • 9 inches long from beak to tail
  • 20 inches from wing tip to wing tip


Breeding Adult

  • white body

  • black cap with white forehead

  • light gray wings

  • yellow bill with black tip

  • yellow-orange legs

Winter Adult

  • paler than breeding birds

  • dark grey eye strip

  • white forehead with dusky brown cap

  • brownish-black bill

  • pale yellow legs

Breeding Adult Interior Least Tern
Breeding adult Interior Least Tern


Juvenile (1 years old)

  • closely resembles winter adult

  • mottled gray-white body

  • white forehead with dusky brown cap

  • dark bill

  • orange-black legs

Juvenile Interior Least Tern
Juvenile Interior Least Tern