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Warmer temperatures are pushing mountain-dwelling birds ever higher as they try to stay in their comfort zone.

That’s the findings of a new study by the University of British Columbia and Cornell Lab of Ornithology scientists who retraced the steps of a 1985 expedition in the Peruvian Andes and documented how birds had shifted in the intervening 30 years.

Scarlet-breasted Fruiteater in Peru. Photo by Graham Montgomery

The study, which appears in Proceedings of the National Academy of Sciences, also shows that species that were already living on the ridge-top now have smaller ranges and some have disappeared altogether compared with the 1985 survey.

Next Stop Extinction

“Mountaintop species are running out of mountain,” says Benjamin Freeman, lead author and postdoctoral fellow at the University of British Columbia.

The researchers found that habitat zones have shifted upslope over the past three decades as temperatures have warmed. Birds responded by moving higher to stay within the zones to which they are adapted. Graphic by Cornell Lab of Ornithology science illustrator Jillian Ditner

“The next step is extinction. Of the 16-mountaintop species found in the last survey, 8 are missing from our new survey.”

Researchers believe there is a high statistical probability that at least four species have been extirpated from the survey area, given the team’s extensive field searches and analyses of audio recordings.

The missing birds are the Variable Antshrike, Buff-browed Foliage-gleaner, Hazel-fronted Pygmy-

Tyrant, and Fulvous-breasted Flatbill.

The Variable Antshrike is one of the species not found by the survey team. Image by Alexander Lees

Climate Change Results in Local Extinction

Though none of these species is considered threatened and they are relatively widespread, this research supports the idea that birds living at higher altitudes in the tropics are moving even higher as a reaction to climate change which can result in local extinctions.

Freeman led the resurvey of Cerro de Pantiacolla, a 4,640-foot (1,415m) ridge in southern Peru, covering the same ground and employing the same methods used in 1985.

Freeman led the resurvey of Cerro de Pantiacolla, a 4,640-foot (1,415m) ridge in southern Peru. Photo by Graham Montgomery

Cornell Lab of Ornithology director John W. Fitzpatrick led the 1985 survey and co-authored the new report.

“This is the first field-work evidence to show that some local bird populations were literally wiped out by upslope shifting,” says Fitzpatrick. “We think this pattern is probably being repeated on tropical mountain slopes all over the world.”

“Since the 1985 survey, the annual average temperatures in the region have increased by around 1 degree Fahrenheit,” Freeman points out.

Ben Freeman and Andean Cock-of-the-rock in Peru. Photo by Graham Montgomery

Climate Change Causes Bird Range Change

As a result, he says that more than two-thirds of the species studied in the research have shifted their ranges upslope an average of 131 feet (40 m) to stay within their habitat.

With Earth’s average temperatures predicted to warm as much as three degrees Fahrenheit more by 2100, tropical species can be expected to shift upslope by another 1,640 to 2,953 feet (500–900m).

The work in Peru follows up a study that Freeman did four years ago in New Guinea that found 70 percent of bird species on a mountain there had shifted their ranges upslope in an attempt to keep pace with climate change.

Deep-blue Flowerpiercer in Peru. Photo by Graham Montgomery

Escalator to Extinction

Taken together, Freeman’s research in Asia and in South America suggests that mountain birds in the tropics worldwide are on an escalator to extinction.

“Tropical mountains harbor thousands of bird species, more than any other terrestrial environment on Earth,” Freeman says.

“Minimizing the effects of climate change on these birds means preserving and restoring forested wildlife corridors at all elevations. Otherwise, we’ll continue to lose mountain species at this very rapid rate.”