Date: 8/3/26 8:51 am From: David Tønnessen <davidtonnessenx...> Subject: [cobirds] Crissal Thrashers in the San Luis Valley
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.
[image: CRTH_maps.jpg]
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.
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