Climate change is likely to affect more than half the bird species in North America in coming decades, shrinking their habitats or forcing them into new, unfamiliar ones, a report says.

By the year 2080, warming temperatures will shrink or shift critical ranges of more than 300 of the 588 North American bird species studied, a report from the National Audubon Society says.

Climate change could impact a huge range of forests, grasslands and other habitats of birds, it says.

"This will spell trouble for most birds," says Gary Langham, the society's vice president and chief scientist.

In just one example, the Baltimore oriole -- state bird of Maryland and mascot of the baseball team -- could vanish completely from the state by the end of the century, the report said.

Eight other states could also find their state birds at risk from global warming, it said.

The report bases its conclusion on 3 decades of bird sightings recorded in the North American Breeding Bird Survey and the Audubon Christmas Bird Count, combined with data provided by leading climate scientists in the United States and Canada involved in the Intergovernmental Panel on Climate Change.

Stuart Butchart, chief scientists for BirdLife International, called the report's results "deeply worrying.

"They add to a body of studies elsewhere in the world showing that climate change is going to have major impacts," he said. "Species are going to have to shift their ranges, and many overall are going to suffer range contraction."

The study researchers said they were unable to discern any reliable patterns to suggest which type of birds might be hit hardest by climate change.

"This is really a species-by-species thing," says Langham.

While one might expect bird species that share a climate-dependent environmental niche -- for example, birds living in grassland habitats -- to have similar responses to changing climate, that's not the cases, he says.

"It's pretty idiosyncratic," he says.

Data on exactly which particular climate factors might drive a species from its traditional habitat is hard to come by, he says.

And while some regions might gains species as habitats change, that will be the exception, Langham points out, because "loss is more certain than gain."

The International Union for the Conservation of Nature currently has 1,373 global bird species -- 13 percent of the Earth's known kinds -- on its Red List of Threatened Species, but that list currently does not take risks of climate change into account, Butchart points out.

The Audubon report "gives us a longer-term view," he says. "It's telling us that a whole additional suite of species will become highly threatened that aren't the ones we're worrying about now."

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