Prairie Falcon

The **prairie falcon** (*Falco mexicanus*) is a medium-large sized falcon of western North America. It is about the size of a peregrine falcon or a crow, with an average length of 40 cm (16 in), wingspan of approximately 1 meter (40 in), and average weight of 720 g (1.6 lb). As in all falcons, females are noticeably bigger than males. Though a separate species from the peregrine, the prairie falcon is basically an arid environment adaptation of the early peregrine falcon lineage, able to subsist on less food than the peregrine, and generally lighter in weight than a peregrine of similar wing span. Having evolved in a harsh desert environment with low prey density, the prairie falcon has developed into an aggressive and opportunistic hunter of a wide range of both mammal and bird prey. It will regularly take prey from the size of sparrows to approximately its own weight, and occasionally much larger. It is the only larger falcon native only to North America. It is resident from southern Canada, through western United States, and into northern Mexico. The prairie falcon is popular as a falconry bird, where with proper training it is regarded as being as effective as the more well known peregrine falcon.

## Description

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). 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 resemble adults except that they have dark streaks on the breast and belly and darker, less grayish upperparts. Calls, heard mostly near the nest, are described as repetitive *kree kree kree…*, *kik kik kik…*, and the like, similar to the peregrine's but higher-pitched.

Experts can separate a distant prairie falcon from a peregrine (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 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.

## Habitat

Prairie Falcons breed in open country throughout the West wherever they can find bluffs and cliffs to nest on, including in alpine habitat to about 11,000 feet. Breeding habitats include grasslands, shrubsteppe desert, areas of mixed shrubs and grasslands, or alpine tundra that supports abundant ground squirrel or pika populations. Breeding birds sometimes forage in agricultural fields. The majority of Prairie Falcons spend the winter in the Great Plains and Great Basin, in habitat that supports the Horned Larks and Western Meadowlarks that make up much of their wintertime diet. This includes grasslands, sage scrub, dry-farmed wheat fields, irrigated cropland, and cattle feedlots, where the falcons also prey on European Starlings.

## Diet

Prairie Falcons in summer eat mostly small mammals, particularly ground squirrels. They also eat pikas, birds, and insects. Prairie Falcons breeding in California and Utah also eat many shorebirds, Mourning Doves, and other bird species. Nesting pairs cache excess prey in clumps of vegetation and rocky areas within their territory, and males and females cache food in separate sites. Such caches provide a buffer against times when finding prey is difficult. In winter most Prairie Falcons switch to a diet featuring Horned Larks and Western Meadowlarks.

## Nesting

During courtship, the male and female spend a month or more visiting potential nest sites together. The site they select is most often in a natural crevice, pothole, or ledge on a cliff or steep bluff, with an overhang to protect the nest. Pairs have also used artificial nest sites dug or drilled into rock faces as part of conservation measures. Most cliff nests are built on the upper half of the cliff face to protect them from mammalian predators. Prairie Falcons also nest in trees, on powerline structures, in caves or stone quarries, and on buildings.

Prairie Falcons do little nest building beyond scratching together loose debris into a small depression or scrape to hold the eggs. They do lay eggs in abandoned stick nests of other species, especially Common Ravens and Golden Eagles.

## Behavior

Prairie Falcons glide with their wings held flat or slightly below the body with wingtips curled up. When flapping to gain altitude, their wingbeats are short and rapid, and the smaller male has a faster wingbeat than the female. Prairie Falcons search for prey from perches, when soaring, and on low-level “strafing” flights, flying as low as 10 feet off the ground. They most often take prey by surprise, gliding on a low approach (or occasionally stooping from high up) to grab a small mammal, bird, or insect in their talons. On the breeding grounds courting Prairie Falcons soar and vocalize together in front of potential nest sites for up to a month before choosing a nesting location. Although pair members roost near each other when courting, the male may choose to spend the night well away from the nest once the eggs are laid. In Oregon, males’ night roosts were located an average of 3 miles from the nest site. During the breeding season, pairs patrol their territorial boundaries throughout the day and attack Prairie Falcons and other raptors that enter their territory, stooping on them and giving a loud kik-kik-kik alarm call while chasing them away. In turn, Prairie Falcons are vulnerable to sometimes-fatal attacks by Peregrine Falcons defending a nest site. Great Horned Owls and Golden Eagles also prey on Prairie Falcon adults and chicks. After the breeding season, most Prairie Falcons don’t migrate directly to wintering areas, but instead “wander” east or even north of their breeding grounds before moving south.

## Conservation

Prairie Falcons are fairly numerous and widespread, although they are hard to survey accurately enough to estimate population trends. According to the North American Breeding Bird survey, populations appeared to be stable between 1966 and 2014. Partners in Flight estimates the global breeding population at 80,000 birds, with 84% spending some part of the year in the U.S., 21% in Mexico, and 5% in Canada. Prairie Falcon rates a 10 out of 20 on the Continental Concern Score, and does not appear on the 2014 State of the Birds Watch List. Prairie Falcons were affected by the widespread use of DDT in the mid-20th century. A metabolite of DTT called DDE causes eggshell thinning, resulting in widespread reproductive failure and population crashes for many avian top predators. Prairie Falcons proved just as susceptible to DDE (or more so) as Peregrine Falcons, but suffered fewer losses because their diet of more mammals and fewer birds exposed them to lower levels of the pollutant. Although it’s illegal to hunt Prairie Falcons, shooting is still a common cause of mortality. Degradation of breeding habitat is also a concern: grassland converted to irrigated agriculture, particularly large-scale monocrops, supports fewer of the ground squirrels that Prairie Falcons rely on. In contrast, smaller-scale agricultural development that offers water and ground cover for ground squirrels can benefit breeding Prairie Falcons. Other factors that impact the birds include extensive wildfires that affect ground squirrel populations, mining development that destroys nesting sites, and human disturbance in nesting areas, including military training activities and road development. Prairie Falcons have benefited from legislation that bans mining and agricultural development in their breeding areas, as well as from the creation of artificial nest sites, limits on human activity near nests, and reintroduction efforts in Alberta and California.