The prairie falcon (Falco mexicanus) is a medium-sized falcon found in Western North America. A separate species from the peregrine falcon, with which it shares some visual similarities, the prairie falcon is, essentially, an arid-climate divergence of earlier peregrine falcon lineage. It is thus able to thrive on a more meager, opportunistic diet compared to that of the peregrine,Pirate of the Plains, Bruce Haak, Hancock House Publishers, 1995, , p.69 and is generally lighter in weight than a peregrine of similar wingspan. Having evolved in harsher and desert environments, often with low prey density, the prairie falcon has developed into an aggressive and opportunistic hunter of a wide range of both mammalian and avian prey, as well as occasional reptiles.The Hunting Falcon, Bruce Haak, Hancock House, , 1992, p. 60 It will regularly take prey from the size of sparrows or finches to birds approximately its own weight, and occasionally much larger.
The prairie falcon is the only larger falcon species native strictly to North America (others are found throughout the Americas and beyond, such as the peregrine falcon with its cosmopolitan distribution). The prairie falcon is resident from Canada (mainly Alberta, British Columbia and Saskatchewan) through the Western United States (west of the Mississippi) and south into Northern Mexico.
Like many raptors and falconiformes, the prairie falcon is popular in falconry; with proper training and care, it is regarded as being equally as skilled as the more well-known peregrine, among others.
Description Appearance Adults
Male prairie falcons are usually 37 to 38 cm in length (~15 inches) and weigh 500 to 635g (1.1 to 1.4 lbs). Females are about 45 cm in length (17.7 inches) and weigh 762 to 970g (1.7 to 2.1 lbs).The Prairie Falcon, Stanley Anderson and John Squires, University of Texas Press, , 1997, p. 8 A large female can be nearly twice the size of a small male, with wingspan reaching to 1.1 meters (3.5 feet), and tends to hunt significantly larger prey.
Plumage is warm gray-brown (sometimes called "sandy") above and pale with more or less dark mottling below. The darkest part of the upper side is the primary wing feathers; the lightest is the rump and tail, particularly the outer tail feathers. The head has a "moustache" mark like a peregrine falcon's but narrower, and a white line over the eye. A conspicuous character is that the axillars ("wingpits") and underwing coverts are black, except along the leading edge of the wing. This creates an effect of "struts" from the body along each wing.
Juveniles There are several ways to distinguish juvenile (first year) Prairie Falcons from adult (second year or older) Prairie Falcons. Each of these methods vary between individuals and several appearance factors may need to be considered as a whole. 1. Vertical dark streaking especially on the upper breast tends to be more prevalent in adults. 2. Exposed portions of shoulder and back feathers tend to be more uniformly colored in juveniles and barred with light and dark horizontal stripes in adults. 3. Skin around eyes, above beak (cere) and on legs and talons tends to be more yellow and sometimes with tinges of orange or green in adults. Skin tends to be gray in juveniles. Factor one can be mistakenly observed because a Prairie Falcon's crop expands and distends upon feeding exposing the white under feathers of the upper breast so that a juvenile Prairie Falcon which just fed can appear from a distance to have a very bright white upper breast like an adult. Also, factor 3 varies so that sometimes a Prairie Falcon's feet begin to turn yellow while juvenile and some individuals have gray skin as adults. It's thought that these fluctuations are caused by diet and resulting hormonal fluctuations between individuals. Of the three factors, factor 2 is probably the most reliable. However, all three factors should be used in conjunction. Interestingly, sometimes one can ascertain whether a Prairie Falcon is exactly in its second year. Some Prairie Falcon individuals molt into adult plumage back and wing feathers that have a more gray tinge than their brown juvenile feathers. First year molts tend to be usually incomplete particularly in the "shoulder" region. If the individual's back and wing feathers have a gray tinge and there are several feathers on the upper wings (shoulder) with a subtle but distinctly different brown tinge, then the bird is a second year bird because it didn't fully molt.
Call Calls, heard mostly near the nest, are described as repetitive kree kree kree…, kik kik kik…, and the like, similar to the peregrine's call but higher-pitched.
Similar birds Experts can separate a distant prairie falcon from a peregrine falcon (generally the only similar species in its range) by its shape and flight style. The prairie falcon has a longer tail in proportion to its size; a more tubular, less stocky body; and the wing joint is farther from the body. Its wingbeats are described as strong and shallow like the peregrine's and having the same quick cadence, but stiffer and more mechanical.Dunne, Sibley & Sutton (1989)
Systematics and evolution Outward resemblance The prairie falcon outwardly resembles the peregrine as well as the Old World "hierofalcons", especially the saker falcon.
Previous categorisation It was previously often considered the only New World member of the hierofalcon subgenus, but in recent decades this assumption has been disproven by genetic analysis. DNA studies beginning in the 1980s have shown the prairie falcon to be closer to the peregrine than to the hierofalcons."Phylogenetic relationships among Falcon species (genus Falco) according to DNA sequence variation of cytochrome b gene", A.J. Helbig et al., Raptor Conservation Today, 1994"Phylogenetic Relationships in the Hierofalco Complex (Saker-, Gyr-, Lanner-, Lagger Falcon)", Michael Wink et al., Raptors Worldwide, 2004
Current classification and convergent evolution It now is considered an early aridland offshoot of the peregrine falcon lineage, much as the hierofalcons represent a laterEarlier results that suggested the hierofalcons to be the most ancient group of living falcons (Helbig et al. 1994, Wink et al. 1998) based on mtDNA cytochrome b sequence data were in error due to presence of a numt in the hierofalcons (Wink & Sauer-Gürth 2000). separate divergence that similarly adapted to arid habitat. Thus, the similarities between the prairie falcon and the hierofalcons are a good example of convergent evolution, with the prairie falcon and similar looking and behaving Old World forms such as the saker and lanner falcons not being the closest of related species, but instead ecological equivalents.Helbig et al. (1994), Wink et al. (1998), Griffiths (1999), Wink & Sauer-Gürth (2000), Wink et al. (2004), Nittinger et al. (2005) However, "closely related" is a relative term here, since most or all the members of the genus falco are closely enough related that they can produce hybrid offspring via artificial insemination. But, only the most closely related of these species will produce fertile or partially fertile offspring.
Relationship to Peregrine falcon The karyological data of Schmutz and Oliphant"Chromosome study of peregrine, prairie, and Gyrfalcons with implications for hybrids", Schmutz S.M. and Oliphant W., Journal of Heredity, 1987, 78:388-390 provided early scientific evidence of the unexpectedly close relationship between the peregrine and prairie falcons. Wink and Sauer-Gürth"Advances in the molecular systematics of African raptors", Wink M. and Sauer-Gürth H, pp. 135–147 in R.D. Chancellor and B.-U. Meyburg (eds.), "Raptors at Risk", World Working Group on Birds of Prey, Berlin, and Hancock House, 2000 later estimated using molecular systematics that the prairie falcon diverged about 3 to 5 million years ago from an archaic peregrine ancestor, assuming a molecular clock calibration of 2% sequence divergence per 1 million years. The prairie falcon then evolved from its peregrine stock forebears in a process of parapatric speciation based on partially separated environments where different selective pressures lead to separate genetic drift and eventually to separate species. This process has led to the prairie falcon having enhanced survivability in the sparse arid environment that dominates the interior of the American west. This enhanced competitiveness in this environment is based on superior energy efficiency (being no larger than the prey base and competition with other raptors requires), and versatility in the utilization of a wider range of prey. Moderately lower weight than the muscular peregrine for similar wingspan not only allows lower food and energy requirements by the simple expedient of less muscle to support, but also allows a lighter wing loading (weight per square unit of wing area) that allows more distance to be covered per calorie consumed when hunting over prey sparse terrain.The Hunting Falcon, Haak, p.60 The lighter wing loading also allows greater maneuverability, which is valuable in the pursuit of agile lightly wing loaded prey and rapidly dodging ground prey. When the prairie falcon locates needed prey, it is relentless in its pursuit. Quoting from the book The Prairie Falcon, "Because they evolved in the harsh western environment, prairie falcons have the stamina to out-fly the strongest quarry. They have the spirit to crash through dense cover when attacking prey, something peregrines seldom attempt."Anderson and Squires, p.114 In the longer distance lower prey density American west, the prairie falcon also has evolved eyes that are proportionally larger relative to head size than the already large eyes of other falcons.Anderson and Squires, p. 25 The specialization of the prairie falcon to this particular environment is also reflected by the fact that there are no subspecies of the prairie falcon evolved to fit other environments, and that it seldom strays far outside the native range to which it is most suited and within which it has competitive advantages over the peregrine falcon.
Though they are separate species after several million years of mostly separate evolution, prairie falcons are known to still occasionally interbreed with peregrines in the wild."Hybridization Between a Peregrine Falcon and a Prairie Falcon in the Wild", Lynn Oliphant, Journal of Raptor Research, 1991 The male offspring of these crossings may be fertile, and provide an avenue for at least some gene flow to possibly still occur between the species. Such gene flow in the past may have contributed to the continuing genetic closeness of the two species today.
Ecology, behavior, and reproduction 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