Endangered Songbird’s Habitat Threatened by Blaze : Wildlife: California gnatcatcher lives in Laguna Canyon, as do coyotes, rats and squirrels. Environmentalists fear the bird’s tiny population may drop without the brush that gave it shelter.

The brush fire that raced through the pristine hills and valleys of Laguna Canyon on Wednesday poses a serious threat to the area’s wildlife, including the rare California gnatcatcher, a tiny songbird which in March was listed by federal officials as a threatened species.

Laguna Canyon runs between Irvine and Laguna Beach and is a key corridor between the beach communities and central Orange County. It includes acres of parkland and pristine wilderness as well as expensive homes. The canyon has been the subject of debate between environmentalists and developers over the construction of roadways and housing tracts.

Environmentalists fear that some of the gnatcatcher’s last remaining habitat may have been destroyed as the fire raced through the canyon, home to many of Orange County’s estimated 250 to 300 remaining gnatcatchers.

It was unclear Wednesday evening whether any birds were killed. The U.S. Fish and Wildlife Service plans to survey the canyon when it is safe.

“We are going to have to assess the impact,” said John Bradley, past president of Sea and Sage Audubon. “I think this definitely means a reduction in the number of gnatcatchers.”

U.S. Fish and Wildlife officials said the gnatcatchers have adapted over the centuries to occasional fires. But with the spread of recent suburban development in and around the canyon, the birds today have few places to go when fire destroys their habitat, they said.

“These birds can fly. But they could fly into areas where there are other gnatcatchers,” Bradley said. “If there are other birds there, they might be scared off. They are very territorial and protect their territory. They will chase off invaders.”

Gerald Braden, a wildlife biologist with the U.S. Fish and Wildlife Service, said he fears that the native coastal sagebrush where the gnatcatchers eat and lay their eggs might also have trouble regenerating after the fire.

He said the native sage will have to compete for space with non-native vegetation that often grows more quickly in the area.

Earlier this year, staff for U.S. Interior Secretary Bruce Babbitt announced that the gnatcatcher would be listed as a threatened species as part of a model agreement between environmentalists and developers that protects the songbird’s habitat while allowing for a limited amount of construction.

Other birds and mammals, including squirrels, rats and coyotes, also faced peril in the flames.

“Some can literally be incinerated if the fire moves fast enough,” Bradley said. “They will also succumb to smoke problems.” The animals who survive the fire will probably have trouble finding food, he added.

Elisabeth Brown of the Laguna Greenbelt open-space group also expressed concern about the fate of old oak trees in Laguna Coast Wilderness Park.

But experts said the fire may also have some positive effects on the area. Bradley said that parts of the canyon will adapt to brush fires and that some seeds won’t sprout unless they are burned.

“It kind of cleans things out. It revitalizes and adds nutrients to the soil,” he said. “Sometimes the brush can get too thick even for some of the animals. In this way, the cleaning out that the fire affords can have some good effects.”