A recent study by the National Audubon Society has found that bird populations -- even those of common, robust species such as grackles -- have fallen drastically over the past 40 years. The populations of whiporwills and bobwhites have fallen by well over 80 percent, a drop so great that these once-common birds are now seldom seen or heard in the eastern US. Deforestation is partly to blame, as well as global warming, which appears to be affecting arctic birds especially hard. Because cold-climate birds must migrate farther north each year to reach their shrinking habitat, they rarely migrate below the northernmost regions of the US.

"These are not rare or exotic birds we're talking about -- these are the birds that visit our feeders and congregate at nearby lakes and seashores and yet they are disappearing day by day," said Carol Browner, Audubon board chairperson and former Environmental Protection Agency administrator in the Clinton administration. "Their decline tells us we have serious work to do, from protecting local habitats to addressing the huge threats from global warming."