The Mojave Desert in California and Nevada has lost 42 percent of its bird species in the past century, most likely due to the effects of climate change, according to a new study.

Researchers from the University of California, Berkeley, did a three-year bird survey in the Mojave that duplicated surveys conducted from 1908 to 1947 by zoologist Joseph Grinnell and his students. The current study showed that the 61 sites resurveyed lost, on average, 43 percent of the species that were there a century ago. The decline occurred across the entire Mojave, but was most pronounced in areas where water was less available, suggesting that dehydration is an important factor in the drop.

Raptors, such as the American kestrel and prairie falcon, experienced one of the steepest declines, but other birds such as the Virginia warbler, mountain quail, and Lawrence’s goldfinch also suffered sharp population drops. The only birds more common in the Mojave today are the common raven and four exotic species, including the Eurasian collared dove, according to the study, published in the Proceedings of the National Academy of Sciences.

The researchers noted that the declines occurred even though much of the Mojave Desert is protected national park or preserve, including Death Valley National Park, one of the nation’s largest. This would suggest, the study said, that a key culprit is today’s hotter and dryer climate in the Mojave.

“The study is clearly showing an erosion of the number of species and the diversity at these sites that is pretty striking,” said Steven Beissenger, senior author of the study and a professor of environmental science at UC Berkeley. “The Mojave Desert is now nearly half empty of birds: Is this a bellwether of changes to come in other protected areas?”