A new study by Colorado State University shows that warming in the high altitudes of the Rockies is apparently having no major impact on the ptarmigan population. Ptarmigan are grouse that like the cold and can often be seen in alpine habitats.
(They’ve been known to hang out around snack bars at ski resorts, scoping the occasional French fry. Don’t feed the ptarmigans!)
Forty-five years of reproductive data for two Colorado populations of white-tailed ptarmigan, one on Mount Evans and the other in Rocky Mountain National Park, were analyzed by Greg Wann, Ph.D. candidate in CSU’s Graduate Degree Program in Ecology and a member of the Natural Resource Ecology Laboratory, and study co-authors, including CSU Associate Professor Cameron Aldridge.
The results, published this month in the journal PLOS ONE, are “surprising,” the authors said, “given the general perception of alpine animal populations as vulnerable to recent climate warming.”
However, the reproduction of the Rocky Mountain National population declined “significantly,” while the birds on Mount Evans remained stable.
“We can’t fully explain this decline (in the park), but we did not find any strong indications it was due to recent warming,” Wann said.
“Climate did affect when ptarmigan bred, and warmer spring temperatures have led to ptarmigan nesting earlier than they did at the beginning of the study in the 1960s,” he said. “We don’t know if earlier breeding will be a good or bad thing for ptarmigan in the future, but our continued research will help address some of these questions.”
“Study authors said predators might be more abundant in the alpine during years with less snow cover, or prolonged hot summers may reduce the abundance of plants that ptarmigan rely on for food,” Mary Guiden wrote, in a story for CSU’s Source. “The team is currently looking at these other factors through a study by tracking individual birds to measure reproductive rates and the associated habitat quality and predator abundance impacts on the number of young produced.”
The white-tailed ptarmigan is the only one that exists in Colorado. The birds are well-known for changing colors seasonally, being mostly brown in late spring and summer, and in molting into a white plumage in fall to match the surrounding snow.