Prairie Falcons use the pockets, ledges and cavities abundant in the rocky faces of the outcrops, canyons and craggy mountains of the Great Basin for their eyries. Either taking advantage of a pre-existing stick nest from perhaps a Common Raven or even a Golden Eagle. Or they use a scrape, a rocky shelf or bowl suited for protecting the adult and eggs during incubation and the young after hatching. If it wasn't for the strings of whitewash, and the subsequent white bibs on rock faces below an eyrie full of nestings, many of these nests would be indistinguishable from their substrates. It is not unusual for a nest to be tucked into folds or hidden within deeper cracks.

The Prairie Falcon begins courtship and copulation in the early Spring. A clutch of normally 4 to 5 eggs can be laid into late Spring. The eggs hatch after 29 to 30 days of incubation and nestlings fledge 29 to 47 days after hatching.

Utah Prairie Falcon Occupation and Nest Starts 2001-2005

Territories are determined as an area held by a breeding pair through the breeding season. More often than not several available ledges, potholes and nest structures are in a territory. In Utah the number of nests in a known territory averages between one and two, but as many as four nest have been found in a single territory. As our efficiency in surveying the area increased so did the number of Prairie Falcon territories. Adult behaviors were the big clues for determining if a territory was occupied and if nesting had begun. Early territory occupation behavior includes a courting pair perching and flying together and exchanging prey, often in mid-air. The female often enters and exits multiple potholes and checks out different nest options. A nest start is determined once she has settled on eggs. Prairie Falcon tend to vocally defend their territory with loud cries from aloft or perched atop a potential nest cliff and also chase away any other raptor or Raven in the general area. Nest starts discovered after hatching also involve interpreting adult behaviors. Once settled on a nest, the streaky head and shoulders of the adult make it nearly invisible against the shadowy walls of an eyrie. However, once the nestlings are able to thermo-regulate, adults spend more and more time away from the nest. Low audible cries from nestlings may be heard from below the nest cliff, while the adults continue to hunt and feed the hungry young. Frequent prey deliveries and feeding give away an unknown eyrie location. The male's arrival in the nest area with a morsel is greeted with the females calls as she takes the prey item and returns to the loudly squealing nestlings.

Utah Prairie Falcon Success & Productivity and Nest Fledgling Production 2001-2005

Nestling development and behavior cues indicate nestling age and probable fledgling dates. Although Prairie Falcon chicks within the eyrie may be very hard to see, in the days prior to fledging they spend a fair amount of time on ledges and perches immediately adjacent to the eyrie. By then much of their plumage has come in and down can be found only on the backs of their heads, and under their wings. A nest is deemed successful once the nestlings reach at least 80% of the species median fledge age (30 days old for Prairie Falcons). All nestlings reaching at least 80% of the mean species fledge age are considered to have fledged, unless observations indicate otherwise. Most mortalities discovered after the 80% fledge age appear to have occurred outside of the nest, post-fledging. Once fledged, the nestlings can soon be found perched and making short coursing flights about the nest cliff. They quickly learn to maneuver and even attempt to chase adults as they deliver food just days after fledging.

Utah Prairie Falcon Trends

The steady increase in the number of known Utah Prairie Falcon territories, occupied territories and active nests (nest starts) suggests that densities of Prairie Falcons increased, but the increase can also be attributed to our increased knowledge of previously used eyries. During the surveys, hatching and fledgling success rates increased even though our fledgling success seems to have stagnated after 2003. The number of total fledglings continued to increase to a record high in 2005. The increase in density (occupied territories) and in nest starts resulted in the record number of total fledgling in 2005. As with most of our focal species, the increased precipitation as the Great Basin comes out of a sustained drought cycle may be a factor in higher success for Prairie Falcons. For more detailed information on Prairie Falcons please see our state specific reports Northwest Utah Nest Survey and Northeast Nevada Nest Survey.