Habitat and distribution The natural
habitat of the prairie falcon is open country, especially arid, in summer including
alpine tundra to shortgrass
prairie and high
desert. In winter it is more widespread, ranging to low deserts and occasionally to towns. It breeds from southern
Saskatchewan,
Alberta and south-central
British Columbia south through the western
United States–roughly between the eastern edge of the
Mountain Time Zone and the
Cascade Mountains, as well as the
Central Valley of California–to the
Mexican states of
Baja California,
Durango, and northern
San Luis Potosí. It is much less
migratory than the other North American falcons, but in winter it does withdraw somewhat from the northernmost and highest-elevation parts of its breeding range and spreads west to the deserts and Pacific coast of California, east to about the 100th
meridian, and south to
Baja California Sur,
Jalisco, and
Hidalgo.
Diet The prairie falcon eats mostly small mammals (especially in summer) and small to medium-sized birds caught in flight, though as an opportunistic predator it will occasionally take larger birds. Though accounts of the prairie falcon taking prey as large as geese are verifiable (a prey that may be over 5 times heavier than a large female prairie falcon), it usually takes prey smaller than itself that it may safely subdue and which can be carried to the nest or to a safe perch to consume. The majority of prey is 150g or less, a weight that even the smaller tiercel (male) can carry long distances back to the nest. Most prey is thus 30% or less of the weight of the tiercel, which is a common prey size fraction across numerous species of falcons where the males do the majority of the hunting during the nesting season. However, over shorter distances wildlife biologists have documented prairie falcons carrying up to about 60–70% of their body weight. Common mammalian prey for prairie falcons includes squirrels, ground squirrels, prairie dogs, chipmunks, gophers, and rabbits of various species. Reptiles are also sometimes taken. Bird prey commonly includes sparrows, starlings, grackles, doves, quail, meadow larks, pigeons, coots, teal, and mallards—virtually any bird of up to approximately the falcon's own size and occasionally significantly larger. However, the need to feed their young focuses them on prey they can carry during nesting season, and the reproductive success of the prairie falcon depends upon such smaller prey being available. Like the
merlin, it often hunts by flying fast and low, at a height of only a few meters or so, hoping to find surprised prey as it comes over the terrain or around bushes. Its cruising speed is estimated at 72 km/h (45 mph) and it accelerates in the chase. A variation on this method is for the falcon to stoop down from altitude and then level out near the ground, initially traveling at more than 100 mph at altitudes of a meter or two, sometimes gliding for more than a kilometer this way. If the rapidly approaching falcon flushes bird prey, the falcon has the speed advantage and may rapidly close with the prey. Another variation on these low attacks is using terrain as cover to approach beneath a flock of birds, then using its speed to perform a rapid climbing surprise attack into the flock. It also pursues prey sighted from a perch in the manner of the short-winged
accipiter hawks, again often flying low and using its speed to close with the prey in a tail-chase. Prairie falcons may even deliberately emulate the flight style of other birds in order to deceive potential prey and allow a surprise attack by the falcon. The dramatic high speed diving stoop from high altitude in the manner of the peregrine falcon, allowing overtaking the swiftest of birds or delivering a knock-out blow to large prey, is also a very natural part of the hunting repertoire of the prairie falcon. At impact the prey is hit with a closed foot or feet, or swiped with an open foot armed with talons. High-speed films have shown that this second method is the more common, with the toes closed into a "fist" immediately after striking. The claw on the hind toe, or hallux, is particularly effective and deadly in raking the prey. When the closed foot strike is used it is typically directed against the head or wing of the prey, and if it does not outright kill, the prey is often rendered unconscious or unable to fly. These strikes are often accompanied by an explosion of feathers and an audible impact that may be heard from the ground hundreds of feet away. They have been known to be so forceful they can literally separate the head from the body of the prey.
Territory Territories of mated pairs in nesting season range from under 200 to over 400 square kilometers. Smaller territories where prey does not have to be carried as far enhances reproductive success.
Nesting Nest This species nests on cliff ledges, so breeding adults are local during the breeding season.
Eggs The clutch averages four eggs, which are subelliptical and pinkish with brown, reddish-brown, and purplish dots. As part of their adaptation to hotter and lower humidity desert climates, the eggs of the prairie falcon are less porous and retain water better than those of their peregrine falcon cousins, leading to a higher hatching rate under these conditions.
Incubation The incubation period is 31 days, beginning with the 2nd to last or last egg laid. Incubation becomes more intense after later eggs are laid, somewhat evening out hatching times.
Splitting of work As is typical for falcons, the female does most of the incubating and brooding, and the male brings most of the food, with the female also hunting after the young are 12 to 14 days old.
Chicks The young
fledge (first fly) from 36 to 41 days after hatching. They continue to be supported by their parents while learning to fly and hunt, with the parents gradually winding down the amount of food they provide as the youngsters' hunting skills improve. At approximately 65 days of age they are ready to be self-sufficient, and disperse from their natal area.
Competition In its range, the prairie falcon must compete for food and space with other often larger raptors including the
peregrine falcon,
red-tailed hawk,
Harris's hawk,
ferruginous hawk,
great horned owl, and
golden eagle. The large, powerful, and surprisingly agile golden eagle is the apex avian predator in this range, and is generally willing and able to attack and kill any of these other raptors. Under the right circumstances all these species are capable of sometimes displacing and occasionally killing the prairie falcon. However, the prairie falcon will aggressively defend its territory against any of them, with male and female often mounting a coordinated attack, and often turns the tables on these larger raptors. Wildlife biologists report numerous observations of prairie falcons successfully driving away and sometimes killing raptors larger than themselves. When a prairie falcon kills a larger raptor, it usually does so in a diving stoop with striking methods similar to what it uses against prey much larger than itself. It may use a foot with talons clinched like a fist to make a high energy strike against the head or wing of its opponent, or use an extended talon in a rapier like thrust to create a fatal wound. However, it is not a given that prairie falcons will always be in conflict with nearby raptors. In years when food is plentiful, prairie falcons have been known to nest within a few hundred meters of great horned owls, peregrine falcons, red-tailed hawks, and golden eagles, with both sets of parents successfully rearing their young.
Population size As of 2006, the population of prairie falcons was estimated to be stable or increasing at over 5,000 pairs, with perhaps 200 pairs breeding at the
Snake River Birds of Prey National Conservation Area in
Idaho. By contrast, in the years before DDT contamination extirpated the eastern U.S. peregrine falcon population in the 1950s and 1960s, the number of eastern peregrines in the United States had already dropped to about 350 pairs. It is thought the prairie falcon mostly avoided the population loss suffered by the peregrine from DDT induced egg shell thinning due to its more remote environment partly insulating it from pesticide contamination. The loss of peregrine population allowed the expansion of prairie falcon range to cliff nesting sites in areas formerly occupied by peregrines moderately outside historic prairie falcon territory. The successful reintroduction of peregrines to eastern and central United States brought peregrine and prairie falcons back into competition in these areas. The reintroduction program led by
the Peregrine Fund bred and released more than 4,000 peregrine falcons from 1974 to 1997. The program necessarily made use of available captive bred peregrine stock with a strong genetic influence from larger bodied peregrine subspecies. The created strain of mixed subspecies peregrine tends to be heavier and stronger than the prairie falcon, and where they conflict over nesting sites they often displace prairie falcons. However, these reintroduced peregrines are little threat to prairie falcon populations within their natural range, as the prairie falcon with its greater heat tolerance, lower daily food requirement, and wider prey base has the survival advantage in the harsh high desert environment in which it has evolved to prosper. ==Use in falconry==