In less than 50 years, some states such as New Mexico, Utah and Arizona, have lost almost half their bird populations.
"Right now, about a third of all bird species in the US are in decline," says Steve Holmer of the American Bird Conservancy, one of the 23 organisations that contributed to the State of the Birds report, the most comprehensive review of bird trends and data ever undertaken in the US.
"The decline points to a very broad-scale problem where we're seeing habitat loss and a variety of threats," he says. "We're particularly concerned about the birds that live in deserts and grasslands in the West, such as the sage grouse. These lands are being heavily used and there's a great deal of oil and gas development, so it's created a huge conservation challenge."
Birds living on the coasts are faring no better. Almost half of all shorebird species, such as ruddy turnstones, red knots and piping plovers, are either endangered or at risk of becoming endangered.
In Hawaii the situation is even worse.
"Hawaii is the extinction capital of the world," says Pete Marra, director of the Smithsonian Institution's Migratory Bird Center. "We've seen about 10 extinctions in the past 40 years and all 33 species of endemic Hawaiian birds are in trouble."
Avian malaria is one of the biggest threats facing Hawaiian birds. The birds have no natural immunity to the disease.
"There are other invasive species there like cats, rats and mongoose," says Marra. "Biologists are working very hard to create enclosures to protect bird populations and keep those invasive species out or even remove them."
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