I was going fishing and birding was a secondary purpose. I decided to cut across the overgrazed prairie to fish the south end of the reservoir. I hadn't walked but a short distance from my vehicle when a group of 9 birds erupted from the prairie and began their soft trills in flight, circling me and eventually landing in a nearby location. I had no doubt these were longspurs as the closest kind of bird like pine siskin would not be in this habitat. Thus began my search and stalking this species for an excellent view and possible photos. As is usually the case, I had brought my junker camera for this fishing day, leaving the better Canon at home. Boy would I regret that! When the birds landed, they vitually disappeared from view? Even with everything overgrazed, they were very difficult to find and get close to. They were very flighty. In and amongst them were numerous Horned Larks and the birds in question were smaller than the Larks.
This is the second occurence of this species in the San Luis Valley and a first-ever for Costilla County. (No records in ebird, R&A, Bailey & Niedrack, Kingery, Wickersham but found one record by Tyler Stuart, 3/27/2016 that was in the CBRC data base for Conejos County). I have kept a bird database for 40 years, and none of the many contributors to those records have ever reported CHLO. I did not bring my good camera. So for 2 hours, I worked this flock of very flight birds as they flew and landed. The birds were smaller than the many Horned Larks in the area maybe 5-6 inches long. They gave a series of shrill trills as they flew. The birds would land on the greatly overgrazed prairie (by hundreds of feral horses that roam the area) and then virtually disappear seemingly into the soil? Where did they go? They were very hard to find amongst the many horse droppings. Finally I got good looks after continual stalking. With a junker camera, I managed to get some decent shots of the birds.
Females were compact, brown sparrow like birds, streaked backs, buffy mostly unstreaked undersides and plain buffy face with slight eye stripe. Male had a distinct white eye stripe and a black eyeline, white throat, buffy patch on cheek, pale throat that broke into solid black breast all the way down to the belly. A bright chestnut collar was visible in certain light. Back was brown and streaked. Crown was dark on male. The flock would flush, circle back to me, and in looking at the tail I saw white outer patches on the tail with an inner portion that was dark. Tail outer edge showed black. There were a few winter male birds too with less pronounced blackish breast and undersides. Initially, I worked a flock of 9 birds. Went fishing for a few hours and upon my return, tallied 15 of them at once.
There were breeding males, winter males and females in this flock.