OAKLAND — "What does a robin look like?"

That's the troubling response that Leora Feeney hears frequently from third-graders after she tells them that the California least tern "is about the size of a robin." Feeney, who worked 30 years as a wildlife biologist, volunteers in the Alameda school district and teaches kids about birds.

"There has been a big change in the past five years," Feeney said. "The robin was always the standard that kids understood."

Third-graders in Alameda County are not the only ones who may not be able to identify robins, grosbeaks, chickadees and sparrows. A growing number of America's most common bird species have declined significantly since 1967, according to a report released Thursday by the National Audubon Society.

"These are not rare or exotic birds we're talking about," said Carol Browner, Audubon's chairwoman. "These are the birds that visit our feeders and congregate at nearby lakes and seashores, and yet they are disappearing day by day." Browner served as EPA administrator in 1993-2001.

For a species to be designated as "common," there must be a population of at least 500,000. The Audubon report states that while these birds "are not in immediate danger of extinction, ... even birds with significantly higher overall populations are experiencing sharp declines. With their populations down sharply, their ecological roles are going unfilled and their ultimate fate is uncertain."

The report attributes the declines to the loss of grasslands, healthy forests and wetlands as habitats, the increase in industrialized farms and urban development, and climate change. Substances such as pesticides can cause secondary poisoning after the birds eat insects and grasses treated with the chemicals. Even increases in certain species of birds, such as Canada geese, can be a problem since they compete for food with other birds.

The report's conclusions are based on the number of birds sighted by tens of thousands of volunteers. The analysis includes data from Audubon's annual Christmas Bird Count program as well as the U. S. Geological Survey's annual Breeding Bird Survey. This is the first time that a report based on both sources has been issued.

Declining bird populations affect the state and the Bay Area, too.

"I've seen a radical decline in recent years," said Elizabeth Murdock, executive director of the Golden Gate Audubon Society. "What humans do, and where we go, is driving this decline in both area seabirds and shorebirds.

"Every time you pull one string of the web in nature, it has consequences throughout the entire system," Murdock said. "That's why we're working to protect bird populations and restore habitats for our native species."

Audubon's report lists California's "five birds of concern" as the northern pintail, the horned lark, the loggerhead shrike, the lark sparrow and the evening grosbeak.

In the Bay Area, some of the bird species in decline include the white-winged scoter, the surf scoter, the canvasback, the California quail, and the olive-sighted flycatcher.

By issuing what it says is a "wake-up call," Audubon officials at the national and local levels stress there is still time to reverse the current trend. Simple steps like planting native plants and those that provide berries and seeds for the birds can help. Pet owners can help by not leaving pet food outdoors that may attract and lead to the growth of predators such as possums, raccoons and skunks.

Leora Feeney says the issue of declining bird populations is bigger than people may realize.

"I'm an avid believer that as people lose their connection with nature, they become less able to solve even greater problems that relate to survival," she said.

Feeney and other conservationists hope the decline in common birds such as robins can be reversed so that future generations will recognize and enjoy them, as these conservationists do.

"Kids used to learn about robins from their families, or from being out in their gardens or backyards. For a number of third-graders not to know what a robin is really raises a red flag."