Out for the Count : Valley birders will help the Audubon Society conduct a census of tricolored blackbirds, which flock to Chatsworth Reservoir.

Valley birders will count tricolored blackbirds Saturday as part of the first single-date statewide census of the species.

Coordinated by the western re gional office of the National Audubon Society, working with the California Department of Fish and Game, the survey will try to determine the number of tricoloreds--a species native to California--and the status of their breeding and foraging grounds.

The census, Fish and Game biologist Lyann Comrack explains, is part of a coordinated effort to make sure that the blackbird, whose numbers appear to have dwindled dramatically over the past 50 years, doesn’t go bye-bye.

Comrack estimates there are between 200,000 and 400,000 of the birds in California. Those numbers sound large, but, as she points out, tricolored blackbirds, unlike redwings, nest in colonies and seem to thrive only when they are surrounded with vast numbers of other tricoloreds.

Loss of habitat is the major reason for the tricolored’s decline, according to Arthur Langton, who will be looking for them at Chatsworth Reservoir.

“We used to have a lot more marshlands once upon a time,” says Langton, a past president of the San Fernando Valley Audubon Society and a physical sciences teacher at Sutter Middle School in Canoga Park. Tricoloreds need wetlands dense with bulrushes, cattails and other aquatic vegetation in order to breed, Langton explains, and most of those have vanished in the increasingly urbanized San Fernando Valley.

Unlike the more common redwings, which are often spotted in pairs, tricoloreds fly around with their fellows. “Great flocks of them disappear into the bulrushes,” says Langton. Tricoloreds can also be distinguished by their markings. Redwings have red and yellow epaulets on their wings, while the tricolored’s markings are red and white. How white? “About as white as you’re going to get on a bird,” Langton says.

The two species also have distinctive warbles. According to Bob Barnes, who coordinates Audubon’s Birds in the Balance program in Sacramento, the redwing has a melodic call, while the tricolored has a braying, non-musical cry that sounds (depending on who’s listening) like mi-a. “It’s like a redwing that’s had its vocal cords messed up,” Barnes says.

Langton has spotted about 200 adult tricoloreds at the Chatsworth Reservoir, which has been allowed to become a 40-acre pond full of cattails and other vegetation ideal for sheltering the breeding birds. Owned by the Los Angeles Department of Water and Power, the reservoir is now a “de facto wildlife refuge,” Langton says. But he fears the blackbirds will be threatened if the city’s chronic fiscal problems lead to the reservoir’s being sold for private development.

The birds travel as far as five miles from their breeding grounds to foraging grounds--usually drier grassland areas--where they “eat any small, crawly insects they can find,” Langton says.

Ornithologists say there are relatively few tricoloreds left in Southern California, especially in the dry inland valleys. Local birders will also count beaks in the Sepulveda Basin and at several sites in the Antelope Valley.

The census was scheduled after a one-day count of the mountain plover Jan. 29 proved to be a great success, tallying more than 3,000 mountain plovers statewide and revealing useful new data on how the birds behave.

For more information about the tricolored blackbird census, contact Bob Barnes, NAS Regional Office, 555 Audubon Place, Sacramento, CA 95825, phone (916) 481-5332 or FAX (916) 481-6228. Or contact Lyann Comrack, phone (916) 657-4436 or fax (916) 653-1019.