In the 1980s, California condors were on the brink of extinction, reduced to just 22 birds. There are now hundreds in the wild, after a captive-breeding program and a decades-long restoration effort. But 20 of the birds in northern Arizona and southern Utah have died of avian flu since March.
The California condor has been endangered since 1967. Half of them have now tested positive for a strain of the avian flu.
Wildlife officials told the Arizona Republic the possibility that the virus could spread to other condor populations is worrying. But it has not been detected in condors in California, or the Mexican state of Baja California.
Experts say migration patterns are aiding spread of avian flu, which has been affecting the birds since last spring. Studies are still underway to determine why this particular strain has lasted longer than others, which tend to die out after a season.
