Colorado birders,
My name is Brett Walker. I'm in the Avian Research section with Colorado Parks and Wildlife. I'm hoping birders visiting the high country over the next couple of weeks might be able to help us get additional information on Brewer's Sparrows breeding in willow and/or conifer krummholz habitats in alpine areas of Colorado (above ~11,500 ft).
As many of you know, there are two known subspecies of Brewer's Sparrows (Spizella breweri) in western North America, the "sagebrush" Brewer's Sparrow (S. b. breweri) that breeds in lower-elevation sagebrush habitats, and the "timberline" Brewer's Sparrow (or "Timberline Sparrow") (S. b. taverneri) that breeds in alpine shrubs (willow, birch, etc.) and stunted conifer krummholz at treeline from Alaska through the Canadian Rockies to northern Montana. However, there have been numerous reports of Brewer's Sparrows at high-elevation alpine sites in Colorado over the past several decades. Both Colorado Breeding Bird Atlas accounts and many Colorado birders have speculated that these birds might actually be "Timberline" Brewer's Sparrows.
We initiated a research project this spring to answer that question. We first compiled historical records of Brewer's Sparrows in high-elevation alpine areas across the state from numerous sources. We then visited a subset of those sites in June to record males' songs and collect morphological data and blood and feather samples from live birds for genetic analysis. We found Brewer's Sparrows in mixed alpine willow/conifer krummholz habitats above 11,500 ft across several mountain ranges in Colorado, from the San Juan Mountains to the Flattops to the Front Range. Several of these sites are already known to local birders (for example, Guanella Pass, Devil's Causeway in the Flattops), but some were new sites.
However, we had limited time and funding, so we wrapped up field work for the project last week, and we were unable to visit many alpine sites where Brewer's Sparrows been previously been reported. We also visited most alpine sites slightly too early this year to confirm nesting. Which is where I was hoping skilled birders might be able to help over the next 2-3 weeks.
If you are experienced with Brewer's Sparrow song and visual identification and can visit 1 or more high-elevation alpine sites to search for Brewer's Sparrows OR revisit 1 or more alpine sites where we found them this year to confirm evidence of breeding between now and July 24 (and report your observations in eBird), your help would be greatly appreciated!
If interested, please contact me ASAP by email (my email is my first and last name separated by a period with "@state.co.us" at the end).
This project was made possible by Colorado Parks and Wildlife, Bird Conservancy of the Rockies (formerly Rocky Mountain Bird Observatory), U.S. Forest Service, National Park Service, eBird contributors, and the Colorado birding community, with special thanks to Aaron Yappert, Tony Leukering, Kim Potter, and John Toolen.
Thank you,
Brett Walker
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