A NEW PERSONAL RECORD FOR MOUNTAIN PRAIRIE FALCONS

I photographed this tiercel Prairie Falcon (Falco mexicanus) this morning during a hike in Utah's Wasatch Mountains, at an elevation a bit shy of 7,000 ft. He had just delivered an unidentified food item to the eyrie site, and I could hear two birds klee-chipping for a moment before he came back into the open (when I took this shot), then left. I never saw the falcon, whom I assume was incubating. March 23 would be an early date for Prairie Falcons in the desert lowlands to be on eggs, but it is a good month earlier than any eyrie I've seen before in the Wasatch Mountains. Falcons are prone to abandon their eggs if disturbed too much, so I retreated after discovering the site. Assuming this pair is successful, it will be easy enough to infer the date incubation began once the young are half-grown.
Prairie Falcons do not build a nest, but normally scrape a depression in the bottom of a cliff pothole. Sometimes, as in this case, they will use an old nest of another bird. This nest was originally built by Bushy-tailed Woodrats (Neotoma cinerea), and has been added to by Ravens (Corvus corax) and Red-tailed Hawks (Buteo jamaicensis), both of which have used the site over the years.
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Photograph by CPBvK, March 23, 2006