'Least terns like an open, flat, sandy area. They like plenty of small fish that they can forage for, and they like solitude. Solitude is the problem," says Chris Redfern, volunteer coordinator for the San Diego Audubon Society. "Terns are very easily disturbed."
Due to population growth in California and gradual development of the coast, the least tern's habitat is shrinking. The California least tern, one of about 35 subspecies of terns, was one of the first species to be listed under the Endangered Species Act. Seventeen "major and monitored nesting sites" exist in San Diego County.
"Least terns find solitude in the weirdest places," says Redfern. The weirdest of which might be Lindbergh Field, where the birds have nested between the runway and the taxiway for over 30 years. "Their concept of solitude is different; they don't want to see any humans or other wildlife that will prey on them or anything that might eat their eggs and chicks."
Aside from having fewer places to nest, terns are threatened by natural enemies including "crows, ravens, coyotes, feral and domestic cats, dogs, and things as small as raccoons, possums, rats, and even ants. Ants can burrow into their eggs." Least tern eggs are about an inch long and are speckled and sand-colored, which helps to camouflage them.
Because eggs are deposited into depressions that have been scratched out in the sand and are not covered over, tern nests are vulnerable. "Ground-nesting birds have it kind of rough," says Redfern. "If there are any predators that find them, they are basically out in the open. You can look right over the fence and see the nests in plain sight," he says, referring to the new black fences that have been erected to protect a nesting area for least terns on Dog Beach.
"The terns went to Dog Beach to avoid predation at other nesting sites like Mariner's Point." Mariner's Point was an unsuccessful breeding location last year because crows discovered the tern nests. If least terns enjoy solitude, one might wonder why they flocked to Dog Beach, a regularly populated area, in the last week of April 2004. Redfern explains, "Historically, the terns would just shift their nesting colony to another site. Since there aren't any more around, they did the best they could. Out of the frying pan, into the fire."
The birds begin nesting in April and leave in the middle of September each year. "We really don't know where they go in the winter," says Redfern. "The western population ranges as far north as Alameda County and as far south as Baja, California. The summer range is concentrated in San Diego, Orange, and L.A. Counties. Chicks are banded, and a few have been found off the coast of Central and South America, so we know they go south, but we don't know exactly where."
The Audubon Society is looking for volunteer docents to help monitor the nesting site on Dog Beach and educate the public. "It's important to keep people 100 feet back from the fence. In 1999 one coyote either destroyed or caused the abandonment of 340 nests at the Santa Margarita river mouth. If one dog gets under a fence at Dog Beach and runs around, or if the terns feel threatened in any way, they may just never come back."
The smallest of their kind, least terns are nine inches from bill to tail. "They are half the size of other terns, which is why they're called 'least' terns," explains Redfern. Least terns are white with gray coloring on their backs and wings and black on the crowns of their heads. Their yellow bills are also tipped with black.
Terns eat small fish, including anchovies and top smelts. "They hover in the air, dive-bomb into shallow water, and grab little, tiny fish." A male tern's ability to fish is part of what determines his sex appeal. When terns first arrive at a nesting area, their first priority is to find a partner and pair up. "A male will go out, catch a small fish, and fly around the nesting site while showing off, calling, 'See, I caught a fish, aren't I great?' He'll cruise around and when he finds an isolated female, he will fly down, land by her with the fish in his mouth, and then parade around her. He tilts his head up, puffs out his chest with male bravado, and struts around her in a circle while he vocalizes 'Kip! Kip! Kip-kip-kip!' in a high pitch." If the female likes the size of the male's fish, she'll get up and follow him in his circular dance. -- Barbarella
Volunteer Least Tern Docents at Dog Beach
June 15 to September 15
8 a.m. to 5 p.m. (Two- to three-hour shifts)
Info: 619-682-7200 or www.sandiegoaudubon.org