ACES Morning Birding at Hallam Lake 10/07/25

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Tuesday, October 7, 2025, 8:00am-11:00am

Weather: Sunny & cold

Location: Hallam Lake, Aspen CO

Frost coated the sedges, grasses, and willow foliage around Hallam Lake this morning. We birded strategically from sunny spots to soak up the sun’s warmth. Crows, a raven, magpies, creepers, and chickadees were active, but otherwise the morning was very quiet. A few mallards showed nearly fully molted breeding plumage, with the males’ iridescent green head feathers shimmering in excellent light. After exploring the Hallam Lake Preserve and immediate surroundings, we went to the adjacent Jennie Adair wetlands where we were immediately wowed by a variety of birds foraging in a loose flock in the willows. A Townsend’s solitaire caught our attention first, followed by a Wilson’s warbler, and then ruby-crowned kinglets, orange-crowned warblers, a Townsend’s warbler, pine siskin, song sparrows, and a yellow-rumped warbler. We were able to observe these birds at close range and in excellent light conditions. The birds actively foraged, hopping and fluttering among the foliage and hovering at tips of branches, and preened – a rare instance in which they sit still and their movements reveal field marks like color of undertail coverts, patterns in tail feathers, eye-rings, and more. These activities allowed us to see all of their subtle field marks, discuss their male/female and non-breeding appearances, and understand the dynamics of this mixed species flock. It was also a special learning opportunity to see the four warbler species side by side, which is only possible during fall migration when they converge at rich feeding opportunities during their journeys. The pine siskin was feeding in a “warbler way” rather than its usual seed-eating “finch way,” leading us to wonder exactly what they were all eating. The birds were picking tiny items from the undersides of the willow and cottonwood leaves, which we discovered were clusters of aphids after picking and inspecting a leaf. This made sense of the siskin’s unusual foraging style, and the fact that it had to work a little harder to eat the aphids than the warblers and kinglets, whose bills and body structures are more adapted to this type of gleaning. Standing there for a full 45 minutes, we felt like we had a special immersion experience, a truly enriching educational moment. Join us for more exciting fall birding next Tuesday at Rock Bottom Ranch!

 

Species List:

~ Rebecca Weiss, ACES Bird Guide

Featured Photo: Townsend’s Solitaire