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Birds that thrive in the proximity of people and dine at backyard feeders delight nature enthusiasts. But the birds sometimes pay a hefty price for their easy meals and use of human structures for shelter. Birds that nest on or around buildings are often disturbed by people and their pets, and nestlings are easy targets for domestic cats.

Now ornithologists have discovered yet another hazard of consorting with humans that can be even more devastating: the ease with which a debilitating disease can spread among birds that congregate at feeders.

Disappearing act

Witness the plight of the house finch, a sparrow-size bird with a reddish breast that is a popular year-round visitor to feeders. In just seven years, some 180 million house finches -- 60% of the population -- have disappeared from the eastern United States, the apparent victims of a highly contagious eye disease. The disease, an infection of the conjunctiva that results in swollen, pus-filled, crusty eyes, can make it impossible for the birds to see.

The house finch, a songbird native to the Western desert, has proved to be highly adaptable, having colonized the Eastern states after its release on Long Island, N.Y., in the 1940s.

With data gathered by thousands of "citizen scientists" who participate in Project FeederWatch, a continent-wide program organized by the Cornell Laboratory of Ornithology, researchers have been able to track the spread of the disease, which now affects finches throughout the East. From November 1994 to February 1996, participants' data tracked the disease, which originated near Washington and spread from Ontario to Florida and as far west as Missouri. The disease is spread when healthy birds come into contact with an infected bird or a contaminated object.

The disease, caused by the bacterium Mycoplasma gallisepticum, seems to have "stalled itself out somewhere in the prairies," said Wesley Hochachka, assistant director of bird population studies at the Cornell laboratory. He and the director, Andre Dhondt, suspect that the distance between populated areas in the Midwest is great enough to inhibit transfer of the disease among groups of birds. As the disease culls the population of house finches, the organism, which lives for only a day or two in the environment, is less able to spread, they said.

Tough to fight

Still, the disease is tenacious. In an article in the autumn issue of Living Bird, Hochachka and his colleagues Dhondt, Sonia Altizer and Barry Hartup noted that the disease was unusual because it has persisted for so long.

# posted by Medical Information : 2:56 AM