An alarming decline in the number of burrowing owls in the Imperial Valley — a Southern California agricultural area that had been considered a stronghold for the species — has prompted calls for an immediate inquiry by state wildlife authorities.
Surveys by the Imperial Irrigation District show the burrowing owl population has dropped from about 5,600 pairs in the early 1990s to 4,879 pairs in 2007 and 3,557 pairs in 2008.
"We've seen a 27% drop in one year alone," said Jeff Miller, a conservation advocate for the Center for Biological Diversity. "If there is a similar drop next year, this bird could disappear in California."
Statewide, the owl has been decreasing because of habitat loss through urban development, elimination of rodents it feeds on, pesticides, predation by domestic animals, vehicle strikes, contact with wind turbines and shooting.
Burrowing owls are between 9 and 11 inches tall and make their nests in holes and tunnels once inhabited by ground squirrels.
Most of California's remaining breeding pairs are concentrated in the Imperial Valley, an area that constitutes roughly 2.5% of the state's land, Miller said. "We still don't know exactly what is causing the declines in the Imperial Valley," he said, "but loss of suitable foraging areas from fallowing of agricultural fields due to water transfers and ground squirrel eradication programs may play a role."
In 2003, the Center for Biological Diversity and other environmental groups, including Defenders of Wildlife and the San Bernardino Valley Audubon Society, filed a petition under the Endangered Species Act to protect the burrowing owl.
The California Fish and Game Commission rejected that petition, in part because it believed the bird continued to thrive in the Imperial Valley and along the lower Colorado River.
"That argument was flawed to begin with," Miller said. "It's time to revisit the issue of state threatened protections for the burrowing owl."