While numbers have gradually increased with its protected status, the species is still vulnerable to population decline through natural disasters, predation, and human disturbance.

Courtship typically takes place removed from the nesting colony site, usually on an exposed tidal flat or beach.

The California least tern hunts primarily in shallow estuaries and lagoons, or beyond the breakers, even beyond 24 km offshore in areas of upwelling, and where smaller fishes are abundant.

In the bays and lagoons of Southern California and northern Mexico, the favored prey include anchovy, smelt, silversides, shiner surfperch and small crustaceans.

Sternula antillarum is also found in breeding grounds along rivers in the midwest and Great Plains of the United States.

Both have conspicuous black markings on their outermost primaries and fly over water with a distinctive hunchback appearance, with bills pointing slightly downward.