North America’s three rosy-finch species – Black, Brown-capped, and Gray-crowned – nest along talus slopes and snowfields up to 14,000 feet, among the highest altitudes for any birds in North America. These uncommon birds forage for insects and seeds on bare soil amid sparse tundra vegetation, traveling in small flocks that, because they seldom encounter humans, can be surprisingly tame. Due to the inaccessibility of their habitat, however, many of the surveys traditionally used to assess trends in rosy-finch populations miss them almost completely. In winter, these birds descend to lower elevations, but their nomadic habits still make it hard to estimate their numbers.
Now, the threat of climate change is spurring new urgency throughout the Southwest to learn more about the health of rosy-finch populations, and predict what could become of them as the snowy reaches where they live warm up.
In New Mexico, all three species can be found in winter at Sandia Crest, near Albuquerque, where they are banded from November through March each year as part of the Rosy-Finch Project, run by Rio Grande Bird Research. In Utah, the Sageland Collaborative also fits birds with leg bands containing microchips that can be “read” by special high-tech feeders hosted by ski resorts, allowing researchers to follow the movements of individual birds over time and estimate their lifespans. (So far, some tagged birds have continued to reappear for three years.)
Meanwhile, the Rosy-Finch Working Group, formalized in 2021 and including representatives from state agencies, nonprofits and universities throughout rosy-finches’ range, seeks to develop improved, standardized survey methods to accurately monitor rosy-finch populations. One study conducted by Colorado Parks and Wildlife and finalized this year found the state has an estimated 115,000 to 150,000 Brown-capped Rosy-Finches – a surprisingly healthy population.
Matt DeSaix, a Ph.D. student with Colorado State University’s Bird Genoscape Project, headed up a recent genetic analysis of Brown-capped Rosy-Finches, with an eye to both the species’ current genetic health and what the future might hold. He and his colleagues sequenced genes from feather and blood samples collected from birds at 11 sites spanning the species’ breeding range. They found no concerning lack of genetic diversity, nor any evidence of inbreeding at any of their sites, supporting the conclusion that the population is robust.
DeSaix’s project combined two methods of forecasting what might happen to rosy-finches in a warming world. His analysis suggests that good rosy-finch habitat will contract and that some amount of natural selection will have to take place for the birds to continue to flourish in the places they currently live. But he cautions that we still don’t know enough about these birds and how they use their habitats to say for sure what will happen.
The Rosy-Finch Working Group is already striving to identify potential ways to help buffer rosy-finches against the worst effects of climate change. Possibilities the group hopes to explore include improving habitat in the birds’ lower-elevation winter ranges by promoting native plants and fighting invasive weeds, and physically removing trees that may encroach upslope into rosy-finches’ winter foraging habitat as temperatures warm.
American Bird Conservancy