U.S. Fish & Wildlife Service

Sacramento Fish & Wildlife OfficeServing the people, conserving the fish, wildlife, and plants of California

A Unit Of The Pacific Southwest Region

Species Information

Photo of CA Least Tern

Photo Credit: USFWS

California Least Tern

Sterna antillarum browni

Basic Species Information

STATUS

listing_process.pdf

Endangered. This species is in danger of extinction throughout all or a significant portion of its range.

We now think the tern should be listed as "threatened." That would mean we are concerned about it, but we don't think it is about to go extinct. We have to go through a legal process (45 KB PDF) to make the change. This is to let people give us reasons why they agree or disagree. The species' population has increased from 600 in 1973 to roughly 7,100 pairs in 2005. The number of California least tern sites has nearly doubled since the time of listing.

DESCRIPTION

The CA Least Tern has a distinctive black cap. It has black stripes running from the cap across the eyes to the beak. These contrast with a white forehead. Other upper parts are gray. Underparts are white. CA Least Terns have short, forked tails. Their bills and legs are orange. When a CA Least Tern is flying, you can see a black wedge on the end of its wings.

As its name implies, the least tern is the smallest of North American terns. It is 21-23 cm (about 8¼ to 9 inches) long. Its wingspan is 48-53 cm (about 19 to 21 inches).

FOOD SOURCES

Food is primarily small fishes, but also shrimp and occasionally other invertebrates. Learn more.

HABITAT

California least terns live along the coast. They nest on open beaches kept free of vegetation by the tide. The typical colony size is 25 pair.

MATING

Most least terns begin breeding in their third year. Mating begins in April or May.

Males perform elaborate aerial displays. After that, they offer fishes to the female. This is called the fish flight display. Nesting starts shortly afterwards in colonies on relatively open beaches kept free of vegetation by natural scouring from tidal action. The typical colony is 25 pair.

The nest is a simple scrape in the sand or shell fragments. Typically there are 2 eggs. Both parents incubate and care for the young. They can renest up to two times if eggs or chicks are lost early in the breeding season.

RANGE

The Pacific Coast of California, from San Francisco to Baja California. See 5-year review (PDF) for detailed, up-to-date distribution information. California least terns winter in Mexico. When feeding, they follow schools of fish and are sometimes seen as far north as southern Oregon.

PREDATORS

Predators include larger birds, mammals such as raccoons and foxes, and domestic dogs and cats. See our 5-year review (PDF) for a detailed list of predators.

THREATS

Dredging, habitat loss, nesting disturbance, pollution, predation by domestic and wild animals. At this point, we don't know whether the West Nile virus will hurt the California least tern. See the University of California Davis web page Potential Effects of West Nile Virus on California Wildlife (5.6 MB PDF). See 5-year review for more specific information about other threats.

WHAT YOU CAN DO

When you go to the beach, pay attention to signs warning you that birds are nesting. Many shore birds nest right on the beach. They are easily disturbed. Don't let your dog chase or bark at them.

Whenever you go to natural areas, observe any signs telling you how to protect wildlife and plants.

You may be able to see a California least tern if you go to the coast.

The California least tern can be seen at several National Wildlife Refuges.

Last updated: November 30, 2017