Bird Maps Over-Estimate Range [LiveScience 2007-12-14]
[Photo] Pinyon Jay (Gymnorhinus cyanocephalus)
If you're looking to spy rare birds by relying on geographic maps in an avian identification book, you may have to look a little harder.
Turns out the maps vastly over-estimate the range of birds, especially threatened or endangered species, according to an upcoming study in the journal Conservation Biology.
“Our study found that species ranges in general tend to get overestimated, but that this trend is particularly pronounced for birds that are threatened, rely on specialized diets or have small habitats,” said study co-author Walter Jetz, a biologist at the University of California San Diego. “This suggests that many threatened species of birds may be even rarer than we believe and are in greater danger of going extinct.”
When Jetz and his colleagues compared typical bird range maps with actual surveys, such as those conducted by the Audubon Society, the scientists found that most species actually occur in only 40 to 70 percent of the range suggested by their range maps.
In other words, these birds are not actually found in 30 to 60 percent of their supposed range. Jetz said that as climate change makes greater impacts on the planet, such maps will have to be far more accurate than they already should be.
“If we’re starting with a range estimate for a population that is much larger than it truly is, then we have started with the wrong parameter for our future projections of climate change,” he said. “If you’ve already started with an overestimate of the range, then there’s a real danger in underestimating the risks of extinction in future projections of climate change.”
??? LiveScience Staff