Study Fuels Debate on Gnatcatcher Rarity

New studies show that 1,800 to 2,100 pairs of California gnatcatchers inhabit Orange and San Diego counties, about twice as many of the songbirds as previously estimated.

The population counts, conducted by biologists working for developers and overseen by a state panel of scientists, intensify the debate over the rarity of the small Southern California bird, which has been proposed for the nation’s endangered species list.

The U.S. Fish and Wildlife Service faces a deadline today for deciding whether to list the species as endangered, but the agency is expected to be granted a six-month extension by the Interior Department.

Environmentalists say the new data, collected from January through March and just released, indicates that the gnatcatcher is rare enough to be declared endangered. Wildlife biologists say the best indicators of a species in peril are not population counts, which fluctuate greatly from year to year, but chronic and severe losses of its habitat and erratic or low rates of breeding.

But Southern California’s building industry says the new surveys show that the federal government has based its proposal to protect the bird on “inadequate and inaccurate information.” Builders oppose listing the bird as endangered because they fear efforts to protect its habitat would stop or delay major developments and roads.

A 1990 report by ornithologist Jonathan Atwood estimated there were fewer than 300 pairs of gnatcatchers in Orange County and 770 to 958 pairs in San Diego County. Studies by Atwood, who has researched the bird for more than 10 years, provide the scientific foundation of the federal government’s proposal to list it.

The new studies, however, found 605 pairs in Orange County during surveys of public and private lands, and from 1,200 to 1,500 pairs in San Diego County. Of the Orange County total, 193 were on Irvine Co. property, 177 were in county parks and 148 were on land owned by the Santa Margarita Co.

No data was collected from Riverside County, San Bernardino County or the Palos Verdes Peninsula in Los Angeles County, which also contain prime habitat for the bird.

For his 1990 study, Atwood did not have access to the developers’ land. This marks the first time that counts of gnatcatchers on privately owned land in Southern California have been publicly disclosed.

The consulting biologists who conducted the surveys were hired by the landowners. But their work was guided by a state scientific panel chaired by Dennis Murphy, director of Stanford University’s Center for Conservation Biology.

Murphy said the numbers were not surprising, and confirm a widespread belief that gnatcatcher populations doubled this year thanks to heavy rains in spring 1991 and last winter. The rains increased the number of insects the birds feed on and improved the condition of vegetation where they breed, he said.

Murphy said the increase does not mean the bird is out of danger. He said a species such as the gnatcatcher can easily double or drop by half in the course of a year, depending on rainfall and other natural conditions.