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Quarter of U.S. Birds in Decline, Says Audubon |
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John Pickrell for National Geographic News |
| November 5, 2002 |
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A quarter of all bird species in the United States have declined in population since the 1970s, according to a report issued by the National Audubon Society. Of more than 800 native U.S. bird species, 201 are included on the group's Watchlist 2000. Frank Gill, Audubon's chief ornithologist, said the report "is the most comprehensive assessment so far of how American birds are declining." The report indicates that some birds, such as the California thrasher (Toxostoma redivivum) and the southeast's painted bunting (Passerina ciris), have experienced population free-falls of 50 percent or more over the past three decades. The population decline has been as high as 70 percent for the cerulean warbler (Denroiica cerulea), found across the eastern United States and especially in Western Virginia, and 80 percent for Henslow's sparrow (Ammaodramus henslowii), which is found in the Midwest. Audubon issues the report periodically to help guide the allocation of conservation resources, especially for bird species that are seriously declining in population or facing threats such as major habitat loss but are not yet listed as threatened or endangered by the federal government. Watchlist 2000 includes more than twice as many bird species as those federally designated as endangered or threatened. The new figure is also twice as many bird species as were listed in the last comparable report by Audubon, which was issued in 1996. The substantial increase can be accounted for in part by a broader survey range—Watchlist 2000 includes birds of Hawaii and Puerto Rico as well as the continental United States—and the use of a slightly different method for assessing the status of birds in the latest report. In a population trend representative of many Hawaiian birds, the report says the akikiki (Oreomystis bairdi), a type of honey creeper on the island of Kauai, has declined from about 7,000 in the 1970s to fewer than 1,000 today. The declining bird populations reflect growing threats to many bird species resulting from habitat loss and fragmentation caused by development and other human activities. Other contributing factors include depleted food sources, the impacts of pollution, incursions of non-native species—particularly on Hawaii—and diseases such as the West Nile virus. Changing Ecosystems Gill said people should understand that the decline or loss of bird and other species occurs in relation to major ecological changes that have potentially broader implications. Bird populations, reproductive rates, and behavior change in response to conditions that also affect the quality of life for people and other wildlife, such as habitat degradation, poor water quality, and depleted fisheries. "The reason for identifying species on the Watchlist is not entirely altruistic," said Gill. "Like the proverbial canary in the coal mine, birds are primary indicators of environmental health, and what hurts birds also hurts the people who share the same space." To compile the report, Audubon researchers synthesized data collected by Partners in Flight, a coalition of ornithological groups; Birdlife International, a global conservation program; and Audubon's own breeding bird survey and annual Christmas bird counts. Details on population sizes, rates of decline, and threats facing birds came from the scientific literature and bird monitoring projects involving members of the public. Observing scientific protocols developed by conservation groups, the birdwatchers provide survey data that, when combined, indicates population sizes over a broad scale. The Audubon report is basically an alert, said Gill. "The Watchlist is preventative medicine," he said, adding that the information should be used to allocate resources toward protecting certain species of birds before they become endangered. The best method of bird conservation is to "keep common birds common," agreed Kenneth Rosenberg of the Laboratory of Ornithology at Cornell University in Ithaca, New York. Audubon's Watchlist and the work done by Partners in Flight is valuable, said Rosenberg, because it promotes proactive conservation of birds that are showing signs of trouble but are not yet at the risk of extinction. "It's far cheaper and more effective to protect and sustain birds before they become endangered," he said. With regulations on species protection directed toward the most endangered birds and other species, those that are not yet endangered but whose populations are seriously declining generally are overlooked, Rosenberg added. Backyard Conservation The major population decline of the cerulean warbler offers an example of the problems many bird species are facing as their habitats shrink and disappear. Today there are fewer and fewer of the forested river valleys that are the warbler's summer habitat, and, as with many other migratory species, the bird's wintering grounds in South America also are disappearing. Yet the news isn't all bad, Gill noted. Some species, such as the bald eagle (Haliaeetus leucocephalus)—widely cherished as a U.S. symbol—and the peregrine falcon (Falco pergerinus), were removed from the latest Watchlist, he noted. Moreover, the rates of decline in bird populations vary greatly across species and regions. "Birds really do rebound when the quality of the environment improves," said Gill. What that means, he added, is that individual actions can have a positive effect. Doing "little things [in the backyard] can make a big difference," said Gill. Examples include planting native plant species to provide food for birds and using pesticides sparingly. Another way to help is participating in surveys of American birds. Efforts to save declining species should exploit people's love of birds, Gill suggested. Bird watching, he noted, has soared in popularity by an estimated 250 percent since the early 1980s; today, about 71 million Americans engage in bird watching, making it the fastest growing outdoor activity. According to the U.S. Fish and Wildlife Service, Americans spent $40 billion last year on activities that involved watching birds and other wildlife, up from $30 billion six years ago. 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