Chamberlain says big mammals such as deer are likely to become increasingly scarce in southwestern California, where the condor is being reintroduced.
"This is now all agricultural land, and it is being developed," he said. "Loss of habitat for large mammals in the Central Valley and southern California would most certainly reduce the possible food sources for wild condors."
Sea lions, meanwhile, are recovering along the Pacific Coast. The California sea lion population is increasing by 5 to 6 percent a year, with total numbers up to around 240,000, according to the U.S. National Oceanic and Atmospheric Administration.
Likewise, harbor seal numbers in California have recovered markedly since the 1970s. The current population is put at 28,000.
If condors can tap into this food source, Chamberlain says, the prospects of the birds spreading across their former West Coast range are "excellent."
"As the seal and sea lion rookeries become reestablished northward, the condors could follow," he added.
Conservationists working on condor captive-breeding and release programs aim to encourage the birds to eat seal carcasses by setting up holding and release sites near these rookeries.
One such site has already been established at Big Sur, California, by the Ventana Wildlife Society (VWS) as part of the California Condor Recovery Program.
This scheme is proving a success, according to VWS executive director Kelly Sorenson.
Sea Lion Meals
"The condors in Big Sur are primarily eating dead sea lions of all ages," he said. "To a lesser extent harbor seals are eaten, and we suspect on at least one occasion the birds found and fed upon a dead elephant seal."
Washed-up whales may also reappear on the condors' menu, Sorenson said.
Although authorities often dispose of whale carcasses before condors get a chance to feed on the mammals, "I believe [whale eating] will eventually happen," he added.
There are a few historical accounts of condors feeding on whale meat. For instance in 1806 the explorers Meriwether Lewis and William Clark saw the birds feeding on dead whales at the mouth of the Columbia River, which empties into the Pacific Ocean at the Oregon-Washington border.
"This bird [flies] very clumsily, nor do I know whether it ever seizes its prey alive, but I am induced to believe it does not," Clark wrote.
The explorer was correct. California condors are "obligate" scavengers, meaning they never kill, eating only the remains of dead animals.
In pre-Ice Age times the condor was found in western North America from what is now Mexico to Canada and in the east from Florida to New York. The bird, which has a 9.5-foot (2.9-meter) wingspan, had retreated to North America's West Coast by the time the first European settlers arrived.
Subsequent pressuresincluding habitat loss, hunting, poisoning by pesticides and lead, and egg collectingeventually restricted the bird to California.
By 1982 just 22 individuals survived.
Since then a captive-breeding program and subsequent releases into the wild have returned the condor to areas of California and Arizona in the United States and Baja California in Mexico.
With its total wild population currently standing at 130, the species remains one of the world's most endangered birds.
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