WASHINGTON (AP) _ A federal judge decided Tuesday that some prime southern California real estate can be had for a songbird.

District Judge George H. Revercomb refused to block the Interior Department from putting the 4-inch bird, the California gnatcatcher, on the endangered species list. If the department does so, it would bar development of the bird's habitat in Orange, San Diego and Riverside counties.

Revercomb denied a request by southern California developers for an injunction prohibiting Interior Secretary Bruce Babbitt from listing the bird as endangered.

Babbitt faces a Wednesday deadline for deciding whether to list the bird as ''endangered'' or merely ''threatened.''

The distinction could mean the difference whether the bird's habitat - 250,000 acres of valuable land spanning the three counties - is precluded from housing development in one of the fastest growing regions of the country.

Babbitt's aides have suggested he may let the deadline pass while officials try to develop a compromise. In a congressional hearing last month, he said he would like to cut a deal that would allow developers use of some of the land while setting aside enough to assure the bird's survival.

Revercomb, a Republican appointed to the bench by former President Reagan, said after a 45-minute hearing Tuesday the developers failed to make ''the showing of irreparable harm'' necessary to enjoin a decision by a federal agency before it is made.

In their suit, the Building Industry Association of Southern California and Orange County's tollway agency contended hat some 4,000 gnatcatchers found in southern California are the same species as 5 million gnatcatchers in the Baja peninsula of northern Mexico.

The U.S. Fish and Wildlife Service has rejected that argument, citing a 1990 study by Jonathan Atwood, a Massachusetts ornithologist, which concluded there are 31 biological differences between the California and Mexico birds.

Attorneys for the developers, claiming that Atwood himself had reached different conclusions just two years earlier, asked Revercomb to prohibit any action until the Interior Department examines and reveals Atwood's raw data.

Christiana Perry, an attorney for the Interior Department, said the ''standard practice'' is for the agency to rely on the best scientific reports available without having to examine the underlying data.

Jerome Falks Jr., an attorney for the southern California developers, said his clients still have several avenues of appeal.

''It's a standoff right now,'' he said after the judge's ruling. ''We just thought it would be more efficient to get the issue (over scientific data) out of the way now. Ultimately, that's still going to have to be decided.''