In the same way that canaries used to warn miners of dangerous gases underground, birds are foreshadowing a global ecological disaster, an expert says.

"Birds, which are quite sensitive to poisons in the environment, serve as an early warning system," Paul Ehrlich, a Stanford University ecologist, said Thursday at the annual meeting of the Peninsula Conservation Center."We are destroying habitats that are vital to our own food resources in ignorance and in the name of development, and the birds are pointing it out to us," Paul Ehrlich,

What is happening to the birds as a result of the deterioration of the environment "presages what will happen to human populations," he said.

It demonstrates a worsening of such widespread environmental problems as toxic contaminations, deforestation, acid rain, pollution of vital bays, estuaries and wetlands and scarcity of clean fresh water, Ehrlich said.

Selenium, mercury and other toxic elements in agricultural runoffs and drainage from power plants and mines are apparently linked to a recent epidemic of bird deformations in the United States, Ehrlich said.

Forest clearing in the East is tied to a decline in warblers and other songbirds, Ehrlich said.

Local deforestation, suburbanization and destruction of winter habitat in South America have reduced the number of some songbirds in the nation's capital by as much as 90 percent from World War II levels; and harvesting old-growth forests in the Pacific Northwest is to blame for decreases in the spotted owl population, Ehrlich said.

The consequences of the destruction of bird habitat in the United States and, to a much greater extent, in the tropics range from climate changes that could alter food production to the loss of vital plant chemicals, Ehrlich said.

"If we don't get a lot of action soon, there may yet be a `silent spring' in our future," Ehrlich said, referring to Rachel Carson's 1962 warning that uncontrolled pesticide spraying would hush songbirds forever.

Duck and loon populations are dwindling where acid rain has wiped out aquatic insects, fish and other prey animals in the birds' breeding grounds, said Ehrlich, author of "The Birder's Handbook," a field guide to the natural history of North American birds.

Florida Bay is running so low on food for the great white herons, the giant birds have taken to panhandling from Florida Keys residents.

"I'm very optimistic about what we could do and pessimistic about what we will do," Ehrlich said, "but we should keep on trying."