Crissal Thrashers in the San Luis Valley

[David Tønnessen]

Birders,

Well, I originally posted this back in May, but it apparently disappeared into the Google Groups ether for unknown reasons. Since Crissal Thrashers are still expanding, let's talk about it.

After multiple failed attempts looking for Crissal Thrasher in far corners of the state, I finally caught up to a few (3!) on the morning of May 15 in Costilla County, in some dry pinyon-scattered sagebrush at 37.012855, -105.513509. During first detection, one individual was giving a song that incorporated imitations of Pinyon Jay, a locally abundant species at this pinyon-littered site, which suggests these thrashers are no immediate newcomers to the area. https://ebird.org/checklist/S339550422

Here are six eBird maps of the Crissal Thrasher progression since 2016 (read left-right, top-bottom), when the northernmost record near Colorado was held by Carl Bendorf from 2011 in Ojo Caliente, New Mexico. 

You might notice that most of the promising progression of this species was originally centered in the Upper Rio Grande Basin--the greater hydrologic/topographic region of what we call the "San Luis Valley" in Colorado. That's where some birders had speculated this species would first make an entrance into the state. That is, until Luke Pheneger and Brian Genge threw everyone for a loop discovering multiples of this species in the far southeast in late 2024, straddling Las Animas and Baca counties. Then the thrashers upended expectations again when Mike Thompson discovered some in the opposite southern corner of the state in Montezuma County, just a few months later in 2025. Finally in April this year, an observant home owner in Costilla County photographed a couple not more than 10 miles from those I had today, completing their San Luis Valley trajectory into Colorado.

Now, as if being among the northernmost Crissal Thrashers in the world weren't enough, the pair photographed in April was at a mind-boggling 8,500 ft. The family group on Old Stage Coach Road were a few hundred feet lower, at 7,800 ft. Cornell's All About Birds lists the species as reaching "nearly 8,000 ft" only in Mexico.

If you do look for these particular Costilla County Crissal Thrashers, please be mindful that they are on private property but can sometimes be viewed from Old Stage Coach Road. They are quite secretive, but at the time were giving quiet songs and diagnostic calls.

Cheers, 

David

David Tønnessen

P.S. These thrashers are among multiple "desert southwest" species creeping into, or very close to entering into Colorado in this part of the state. A Greater Roadrunner was photographed 6 miles south of the border here in 2020, and Canyon Towhees are reported regularly 10 miles south. Curve-billed Thrashers seem to be regular further south, but this is complimented by a bird photographed by Luke Pheneger and Brian Genge in Alamosa County last year, although that bird was almost certainly a vagrant.

[David Tønnessen]

Thanks to David Suddjian for letting me know, it seems the maps image didn't fully make the journey; here are the maps referenced.