Hallam Lake in Winter Belongs to the Birds, and to the Count That Starts There

Where does a songbird that feeds underwater go when an Aspen lake starts to freeze? At Hallam Lake, on the morning of December 2, 2025, the answer was a narrow channel near an old beaver food cache. An American Dipper perched on the edge of the ice and on submerged rocks there, and swam the small stretch of water that stayed open.

That detail comes from a field report by Rebecca Weiss, the ACES bird guide who leads the winter outings at the preserve. It explains why the 25-acre preserve at the end of Puppy Smith Street matters more after the wildflowers are gone. Hallam Lake has moving water, mature cottonwoods and conifers, and a staff naturalist on site. In winter that combination makes it the West End's bird station, and on January 3, 2027, it is where the 127th Aspen Christmas Bird Count meets before heading out.

The Water That Stays Open

The preserve sits behind the Aspen Post Office. A set of stone gates marks the entrance, with parking on the left, and a trail runs from there down to the Hallam Lake Nature Center. Elizabeth Paepcke donated the property in 1968, and it was the first home of the Aspen Center for Environmental Studies.

The winter birding depends on how the water behaves. On that December 2025 morning the new snow had started the season's snowpack on the valley floor. Mallards in fresh breeding plumage dabbled on the upper pond and the lake, and a few fed in the small rivulets that run into the lake system. A hatch-year Great Blue Heron hunted in the shallows, and part of the group saw a Belted Kingfisher. All of those birds need water they can reach through or around the ice. The rivulets, the channels and the shallow edges are what hold them at the lake.

On that same outing the group walked the lower Hunter Creek Trail and watched anchor ice forming in Hunter Creek. Weiss describes anchor ice as super-cooled water and frazil ice particles in turbulent water sticking to rocks on the streambed, where more ice builds on them. Her report also notes that ice floats because it is less dense than water. That keeps conditions livable under the surface all winter, including for the invertebrates that birds eat.

What Two Recent Lists Recorded

ACES posts a species list after each outing. This October's list and last December's, taken together, show what a winter walk at Hallam Lake is likely to turn up.

October 20, 2026, mostly sunny, 8 to 11 a.m.

• Brown Creepers, seen and heard again and again in the cottonwoods
• American Dippers feeding along the lakeshore and behind the raptor building
• A flock of Red Crossbills in the cone-bearing spruce
• Wilson's Snipe, Hairy Woodpecker, White-breasted and Pygmy Nuthatches, Ruby-crowned Kinglet and Lincoln's Sparrow, among 19 species in all

December 2, 2025, cloudy with light snow

• Canada Goose, Mallard, Great Blue Heron and Belted Kingfisher on the water
• Black-billed Magpie, Steller's Jay and American Crow
• Black-capped and Mountain Chickadees, Pygmy Nuthatch, House Finch and Song Sparrow
• One American Dipper in the open channel

The dipper, the heron, the kingfisher and the Mallards appear on both lists, taken about ten and a half months apart. They are the birds tied to the open water. For the October list, Weiss's report says the species count was short and the observations were unusually rich. That fits the program's own description of winter birding. With summer's leaves gone the views are better, and birds gather close together around food sources.

Birds are not the only animals in the preserve. ACES's list of what roams there includes mule deer, elk, foxes, coyotes, bears, beavers, golden eagles and hawks. Visitors can borrow ACES binoculars, and the trail is a half-mile loop through wetlands, aspen forest and meadow with stops at several observation decks. A naturalist is on site to answer questions, and ACES says winter is a good season to learn animal tracks. Winter hours for Hallam Lake run Monday through Friday, 9 a.m. to 5 p.m., from October through May, and ACES describes the preserve as open to the public year-round. For anything the website doesn't cover, the front desk number is 970-925-5756.

The Guide Behind the Lists

The monthly outings are led by Rebecca Weiss. She has guided birders in the Aspen area for thirty years and wrote the local guidebook Birds of Aspen and the Roaring Fork Valley. She first came to ACES as a summer intern in 1993, and her background includes bird banding, field research and work with the National Park Service and the U.S. Fish & Wildlife Service.

Because she writes up every outing, ACES's blog works as a running record of the lake through the season. Each walk adds a dated species list to the archive, and the one before the bird count shows which birds are in the area just before the census.

Hallam Lake's Winter Calendar, From December Into April

The program calendar leads up to the bird count in January and then continues through the cold months. Every item below takes place at Hallam Lake.

Morning Birding runs on the first Tuesday of each month from November through April. Because outings require registration by 5 p.m. the day before, the Winter Birding page is where to confirm each month's date. The sound bath series has two more dates, January 26 and April 20, held at ACES's Toklat location instead of the lake.

January 3: The Count Leaves From the Stone Gates

The 127th Annual Christmas Bird Count is part of the Audubon census that ACES calls the longest-running citizen science survey in the world. It has been run since 1900, and more than 50,000 people across the Western Hemisphere take part each season. Audubon's count period runs from December 14 to January 5 each year, so Aspen's count falls near the end of that window.

On the morning of the count:

1. Volunteers meet at Hallam Lake at 7:30 a.m., where ACES explains the counting methods.
2. The group splits into four routes that together cover a 15-mile-diameter circle around Aspen, and birders carpool between routes.
3. The count wraps up mid-afternoon. ACES asks participants to bring water, snacks, binoculars or a borrowed ACES pair, and warm layers with footwear suited to some walking.

Birders of all experience levels are welcome, and anyone collecting data is asked to register. West End residents can also help from home. ACES takes registrations for bird feeders inside the Aspen count circle and accepts feeder-watching and count-week observations. Questions go to [email protected].

Last season's results give a baseline. ACES reported that the December 14, 2025 count had 31 participants and tallied 1,196 birds across 41 species. The circle usually averages in the mid-40s for species, and ACES connected the lower activity to that month's warm, dry weather. Highlights on count day were a Northern Shrike, two Wilson's Snipes and a Clark's Nutcracker. White-tailed Ptarmigans and an American Goshawk were recorded during count week. Wilson's Snipe also appeared on Hallam Lake's own list this October, so the 2027 count has a recent local sighting to compare against.

When the Season Moves Uphill

From mid-December, ACES also offers naturalist programs on the ski mountains. Guided snowshoe tours on Aspen Mountain run daily at 10 a.m. and 1 p.m. from December 14 through April 16. The Snowmass tours follow the same schedule from December 14 through April 9. Each tour lasts two hours, costs $90 for adults or $66 for youth and seniors, and includes the gondola ride, snowshoes, instruction and a guide.

The mountain tours end in April, the same month as the last Morning Birding outing and the last sound bath at the lake. Until then, the open channel near the old beaver cache is the place to look for a dipper.

At Palladium Group, we see Hallam Lake as part of what makes the West End feel like home in the quiet months, a 25-acre preserve a short walk from the post office. If you would like to talk about the West End through the seasons, please request a private consultation.