Seeking cause of condor's decline

In the mountains just northeast of Los Angeles, two men - Noel Snyder and John Ogden - are waiting day and night for the right moment to catch a condor. They are not hunters, but biologists. They are codirectors of the Condor Research Center, a joint project of the US Fish and Wildlife Service and the National Audubon Society.

The project is aimed in part at finding out why the California condor population has been declining at a net rate of two or three birds a year. It also aims at increasing the existing supply, as efforts to breed birds in captivity continue.

The California condor, a black North American vulture with a 10-foot wing span and distinctive white patches under each wing, is an endangered specie. The total population, which spends both winters and summers near the San Joaquin Valley, is now a well-documented 24 birds. Two of them were born within the last month from eggs taken from the wild and incubated in the San Diego Zoo. Two more babies are expected to peck their way out of eggs in May.

The condor-catching team, which includes a number of volunteers and part-time workers, are hoping that their 50-foot-square net trap (using an animal carcass as dinner bait) will catch a female bird, which can then be transferred to the Los Angeles Zoo for breeding purposes. That is where Topa Topa, the first male bird captured, in 1967, now makes his home. Wildlife experts had hoped to return him to the wild, but he did not take well to the return.

If the field biologists lying in wait happen to catch a male, they will put a small, solar-powered transmitter on one wing so they can more efficiently track his flight paths and routine social and mealtime behavior. Most tracking has been done by car and airplane, but condors often move 80 to 100 miles on one quick flight. If a bird with a transmitter should be injured or fall, or even if he just abruptly changes location, the radio signal picked up by receiving stations in the field can help the trackers find him much faster.

The wings of two other male condors were tagged with radio transmitters last fall, and the ultimate hope is to equip 10 or 15 condors, according to Randy Perry, who heads up the project from the Patuxent, Md., research center of the US Fish and Wildlife Service.

In time, the signals picked up will be analyzed by a computer at the project's Ventura, Calif., base and transferred to the Patuxent facility for storage. For the moment, however, the only computer keeping constant watch on the signals is in William Cochran's basement in Champaign, Ill. Mr. Cochran, a bird-tracking specialist with the Illinois Natural History Survey, was trained as an electrical engineer and developed the radio transmitters used in the condor project.

He has been tracking a variety of birds by radio signal for so long that he can tell by the sound whether or not the bird is gliding (a steady signal), circling (a signal that fades in and fades out), or climbing to cooler air (the pitch goes up).

He says he checks on signals from the condors three or four times a week, and he recalls getting a request about a month ago from one of the California trackers to pin down the whereabouts of the younger male that had been tagged. The tracking airplane was out of commission and the field worker didn't want to drive 100 miles out of his way if the bird had zipped off in another direction. Cochran's siting, from 2,000 miles away, saved the man a half day's drive.

''The signals really allow for constant and relatively effortless monitoring, '' he says. ''The computer never goes to sleep.''

There are a number of theories as to why the number of condors has been declining. Some blame random killings by frustrated hunters; others say some birds may be colliding with power lines; others speculate that the condors are being poisoned by pesticides, pollution, or from eating carcasses of squirrels poisoned by ranchers.

Certainly one factor in the low survival rate is the unusually long time (6 to 10 years) required for condors to reach sexual maturity and produce offspring. Unlike most birds, they produce only one egg a season. But researchers have found that if that egg is removed from the nest early on, the parents will usually breed again and produce a second egg. Fish and Wildlife researchers discovered this by working with the more plentiful Andean condors for the last 15 years.

Those involved in the project say they hope the radio signal system will in time verify one or more of the explanations for the decline.

''We'd like to get some hard data instead of just operating on hunches,'' says Inez Connor, a Fish and Wildlife Service spokeswoman. ''We have a lot of clues, but we need to be able to fit the pieces of the puzzle together so we can help.''

Though the project has had congressional approval and federal funds from its start in 1979, it has been decidedly controversial - one reason it took California field workers several years to get trapping permits. Some conservationists have argued that protection of condor nests and feeding areas from urban sprawl is the best help man could offer. They say any other efforts, such as trying to hatch eggs in captivity or attach wing transmitters, may adversely affect normal condor behavior, including breeding habits.

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