ACES Rosy-Finch Study at Snowmass Village 03/11/25

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Tuesday, March 11, 2025, 8:00-11:00am
Weather: Sunny and mild
Location: Snowmass Village, CO

Late winter brings large flocks of rosy-finches, North America’s highest altitude birds, to certain residential and ski area bird feeders in the high mountain valleys of the Southern Rocky Mountains. These highly specialized birds nest in craggy rock faces on peaks and ridges as high as 14,000 feet elevation during the brief mountain summer season. There, they are mostly spread out over their rugged habitat, although they sometimes nest in loose colonies. It takes a lot of effort to find rosy-finches in the summer, but in winter, they can be observed at close range as they feed on sunflower seeds at bird feeders. For those who ski at Snowmass, the rosies are pretty reliable on most days at the Wildlife Center on Elk Camp or at Sam’s Knob, where feeders are stocked regularly. ACES organized this rosy-finch study at a private residence in Snowmass Village, where we were able to observe a flock of 300+ rosy-finches from various angles for different lighting on these beautiful birds. It was such a treat to see them in numbers, where we could compare their subtle field marks, identifying species, forms, males, females, and first-year individuals. At this study, two species of rosy-finches were present: brown-capped, which is nearly endemic to Colorado, and gray-crowned, of which two forms were present (Hepburn’s and interior). Black rosy-finches typically join these mixed flocks in low numbers, but they were not present during our outing.

We discussed the unique life history of the rosy-finches and how they adapt to their extreme, low-oxygen environment. We talked about their insect and seed foods, and the ways they forage at edges of receding snowfields and where mountain air currents deposit insects on the snow surface. We also discussed their conservation status and the challenges they face with climate change. Like bristlecone pines, these birds are so well-adapted to the cold, harsh, extreme conditions of the high mountains that they rely on these conditions for their survival. We discussed findings of recent research on rosy-finches, about whom relatively little is known due to the inaccessibility of their habitats. Fortunately, the brown-capped rosy-finches of Colorado show strong genetic health and it is thought that their population is fairly stable at this time.

Join us on March 18th for a winter birding outing at Toklat in the Castle Creek Valley, where we hope to see more local winter birds, with a special focus on red crossbills and pine siskins, and their fascinating life histories.

Species List:

~ Rebecca Weiss, ACES Bird Guide

Featured Photo: Rosy-Finch