Abstract
Recent observations of the critically endangered California condor indicate an apparent reduction in the number of breeding pairs from five last year to only two this year, the U.S. Fish and Wildlife Service and the California Department of Fish and Game reported today.
Although nesting activity should have begun in the past two months, researchers at the Condor Research Center in Ventura, California, have observed only single adult condors in the territories of three of the pairs that nested in 1984.
In addition, at a fourth breeding territory, one of the pair is missing, but its mate has apparently formed a new pair bond with a different bird. This pair is expected to produce an egg soon.
Biologists are concerned that the missing birds may have died. If so, the wild population of condors may now consist of a minimum of 11 birds. Through October 1984, biologists estimated a minimum of 15 condors in the wild population, including the five known breeding pairs, two subadults not yet old enough to breed, and three unpaired adults. Final count of the 1985 population will be made in September when distinctive feather patterns are apparent, allowing biologists to identify individual birds.
Nine condors have been outfitted with radio transmitters since 1982 to enable biologists to track their movements, but only one of the condors now missing had a radio transmitter. Researchers are receiving no signals from its transmitter and so are unable to trace the bird. A second radioed bird died last year; biologists were able to locate it from the radio signals and later determined that it had died of lead poisoning after consuming a bullet fragment that was probably contained in the carcass of an animal the condor ate. This leaves seven radioed condors in the wild.
One of the remaining breeding pairs has already laid two eggs this year. The first egg, laid in mid-February, was taken by biologists to the San Diego Wild Animal Park, where it is expected to hatch in April. Removal of an egg is known to stimulate production of a second egg - a technique known as "double clutching" - and this pair has just produced its second egg, which was also taken to the San Diego facility on March 19.
The apparent loss of three of the breeding pairs follows a highly successful breeding season during 1984. Last year the five condor pairs - encouraged by researchers to increase their normal .rate of reproduction through "double-clutching" - produced a total of nine eggs. Eight of these were removed from the wild and hatched in captivity at the San Diego Zoo; they produced six healthy, surviving offspring. The ninth egg hatched in the wild and the chick was later captured and taken to the Los Angeles Zoo. Altogether, there are now 16 condors in captivity at the Los Angeles and San Diego Zoos, including the eggs and nestlings taken during 1983 and 1984 and an adult male that has been in captivity since 1967.
The taking of the eggs and nestlings into captivity is part of the long-term recovery plan for the condor, which calls for establishment of a captive breeding flock whose offspring would eventually be released to supplement the number of wild condors. The restoration of a viable wild population is the ultimate goal of the recovery program. However, only one of the 16 condors now in captivity is old enough to breed. It will probably be at least another five years before offspring from these captive birds would be available for release.
For the captive breeding program to succeed, however, the birds that will be bred cannot be too closely related. Thus, researchers planned to continue taking eggs and nestlings produced in the wild into captivity until they had a sufficient number of birds of both sexes and different parentage to give a good assurance of success. At the same time, they planned to release young condors now in captivity that would not be needed for the breeding program. Under current plans, three young condors would be released later this year, pending success of this year's efforts to obtain an adequate number of wild-laid eggs for hatching in captivity.
The California Condor Recovery Team...