Falco della prateria

Identificazione

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.<p>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.<p>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.<p>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.<p>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.

Tassonomia

Nome scientifico

Falco mexicanus

Autorità

Schlegel, 1850

Ordine

Falconiformi

Famiglia

Falconidae

Genere

Falco

Areale e habitat

Migrazione

Nomadic movement

Conservazione

Due to this species' large range and apparently increasing population, it has been classified by the IUCN as least concern. However, it has experienced some local declines in Texas, California, British Columbia and Alberta as grasslands are developed for agriculture, suburbs, highways, and other automobile uses. Such a decline could result in an inability for birds to find mates or suitable habitats.

Tendenza della popolazione

rising