Scientists have recreated a 1985 study of birds in Peru that shows climate change is pushing them from their natural environment. Thirty years ago, researchers studied more than 400 kinds of birds living on a mountainside in Peru. In 2017, researchers looked again at the bird populations. They found that almost all had moved to higher places in the mountain. Almost all had decreased in size. And, the scientists say at least eight bird groups that started at the higher elevations had died out completely. John W. Fitzpatrick is director of the Cornell Laboratory of Ornithology and a co-writer of the study. He said, “Once you move up as far as you can go, there’s nowhere else left.” The researchers say the birds might have moved up the mountain because of temperature changes. Or, they say, changes to food sources may have forced them to go higher. The findings were published in the Proceedings of the National Academy of Sciences.