Family Falconidae
falcons and caracaras
(Also: falcons)

The Falconidae is one of two families within the order Falconiformes. Falconidae contains 11 genera and 64 species, and is divided into two subfamilies, Polyborinae (caracaras and forest-falcons) and Falconinae (true falcons and falconets).

Falconids can be found in most terrestrial habitats throughout the world, but the greatest diversity of falconids is found in South America and Africa. All falconids are able hunters that can take a variety of prey, including insects, birds, mammals, herpetiles and carrion. Most falconids are solitary and territorial, though a few species are colonial or semi-colonial. All but one species is monogamous, and pairs breed once per year, raising between one and six chicks. Both the male and female provide parental care, with the male providing the majority of food for the female and nestlings. ("Falcons and Caracaras (Falconidae)", 2002; "The Howard, Moore Complete Checklist of the Birds of the World, and Third Edition", 2003; Kemp and Newton, 2003; Sibley and Ahlquist, 1990; Snyder, 2001; White, Olsen, and Kiff, 1994)

Falconids are native to terrestrial ecosystems worldwide, except in the high arctic and on Antarctica. Africa and South America host the highest diversity of falconids. ("Falcons and Caracaras (Falconidae)", 2002; Kemp and Newton, 2003; Snyder, 2001; White, Olsen, and Kiff, 1994)

Falconids are found in nearly every terrestrial habitat, including dessert, tundra, taiga, grasslands, savanna, scrub forest, chaparral, forest, mountains, coastal areas, wetlands, estuaries, lake shores, agricultural areas, suburbs and cities. The highest diversity of falconids is found in the tropics, in open rather than forested habitats, and in lowlands rather than at high elevations. Most species are adaptable to various habitats, as habitat structure and availability of nest sites appear to be more important than specific vegetation. A dramatic example of this adaptability are peregrine falcons (Falco peregrinus) and kestrels that successfully breed in cities, nesting on tall buildings and other man-made structures and hunting pigeons and other urban wildlife. Other species, including most forest-falcons in Polyborinae, require more specific habitat, such as undisturbed forest interiors. Migratory species often choose winter habitat that is similar in structure to their breeding habitat. Males, females and juveniles of some species may winter in different habitats, the juveniles taking advantage of habitats with abundant prey but an absence of nest sites. ("Falcons and Caracaras (Falconidae)", 2002; Cade et al., 1996; Snyder, 2001; White, Olsen, and Kiff, 1994)

The family Falconidae has historically been placed with the family Accipitridae (hawks and allies) in the order Falconiformes. While some authors, based on various morphological, biochemical and genetic evidence, have suggested that Falconids are closely related to Strigiformes (owls), Ciconiiformes (storks and relatives), Cathartidae (New World vultures), Psittaciformes (parrots) or Cuculiformes (cuckoos and relatives), most modern taxonomies continue to place them in Falconiformes with Accipitridae. Within the family Falconidae, the relationships between taxonomic groupings are unclear. ("Falcons and Caracaras (Falconidae)", 2002; "The Howard, Moore Complete Checklist of the Birds of the World, and Third Edition", 2003; Griffiths, 1999; Sibley and Ahlquist, 1990; White, Olsen, and Kiff, 1994)

Falconids are medium-sized to large birds of prey (wingspan 55 to more than 125 cm, weight 28 to 2100 g), typically with hooked beaks, large brown eyes and a yellow cere, eyerings and feet. Falcons (Falconinae) are typically stocky birds with pointed wings, long toes with sharp talons, hooked, notched beaks, and brown, black, gray or white streaked or mottled plumage. Caracaras (Polyborinae) are smaller than falcons, have longer necks and legs than falcons, thicker, flatter talons, more rounded wings, a semi-bare face that is often brightly colored, and often glossy black plumage. Plumage of most falconids is lighter below and darker above. Individual species show variation from the basic structures that reflects the functions required by their habitat and prey. For example, the length and strength of the toes and beaks vary widely within the family and correspond to prey type. Bird predators have long toes, where as insect- and mammal-catching species have shorter, fleshier toes. Wing shape also varies; fast, open-country species have long, pointed wings, whereas forest-dwelling species have more rounded wings and longer tails.

Like other birds of prey, falconids exhibit reversed sexual size dimorphism (females are larger than males). This trait is most exaggerated in falconids that catch fast-moving prey, such as birds, and less pronounced in species that primarily eat carrion. In some species, females may also have a larger bill than males. Sexual dichromatism occurs in a few species of falconids. Male and female plumage are similar in most species, though male plumage may be somewhat brighter. Immature falconids typically exhibit plumage that is dull in color, often brownish with pale edges and more streaked than adults. Some species, such as gyrfalcons exhibit light and dark morphs. Falconids molt once per year, and immatures of most species attain adult plumage by the first annual molt.

Traits shared with Accipitrids, the presumed sister taxa of falconids include a fleshy cere covering the base of a strongly hooked beak, strong hallux (hind toe) opposing three forward toes, habit of capturing prey with feet, and reversed sexual size dimorphism (female larger than male).

Traits that distinguish this group include a tubercle (small, bony projection) in the nostril, structure of the syrinx, characteristic flight-feather molt pattern, tomial teeth on bill for killing and dismantling prey, chemical composition of eggshells, reddish (rather than blue or greenish) translucence of eggs when held up to light, and habit of killing prey with the beak (rather than squeezing with the feet). ("Falcons and Caracaras (Falconidae)", 2002; Kemp and Newton, 2003; Snyder, 2001; Wheeler and Clark, 1995; White, Olsen, and Kiff, 1994)

Estimates of annual adult survival ranges from 65 to 80 %. The highest mortality probably occurs during the first year. Some of the oldest known falconids include a crested caracara (Caracara cheriway) and a peregrine falcon (Falco peregrinus), both of which lived to 22 years old. ("Falcons and Caracaras (Falconidae)", 2002; Snyder, 2001)

Falconids can be sedentary or migratory (or partially so). Of those species that do migrate, some fly long distances (up to 20,000 km) between breeding and wintering grounds, and others make only small shifts, such as changing elevation from a high-altitude breeding territory to a lower-altitude wintering ground where food is more abundant. Some species are partially migratory; only part of the population migrates when food becomes less abundant. For example, females of some kestrels migrate while the males stay on the breeding grounds year round.

Most species of falconids are diurnal, though some are crepuscular. Individuals usually have a regular spot where they return to roost at night. Falconids spend considerable amounts of time maintaining their plumage, preening and bathing in dust or water, presumably because the condition of their plumage affects their ability to catch prey. Falconids are generally strong, powerful fliers. Some of the most spectacular fliers are peregrine falcons (Falco peregrinus), which can reach speeds of up to 180 km per hour in a stoop (steep diving flight).

Most species of falconids are solitary and territorial. However, others are gregarious, flocking together opportunistically to feed, roost, breed or migrate. One species, red-throated caracaras (Ibycter americanus), live in cooperative groups and defend a communal territory. Falconid social behavior may change throughout the year, some species become more gregarious outside of the breeding season. ("Falcons and Caracaras (Falconidae)", 2002; Snyder, 2001; White, Olsen, and Kiff, 1994)

Falconids use calls to advertise ownership of a territory, to communicate between mates or group members, and in territorial or food disputes. Pairs of breeding forest-falcons sing duets before sunrise, a behavior that presumably functions to advertise their occupation of a territory, and perhaps to strengthen the pair bond. Chicks and females also use vocalizations to beg for food. The vocalizations of falconids are simple, repeated monosyllabic calls, described variously as cackles, chatters, squawks, croaks, wails and whines. Other behaviors used to communicate include flight displays, such as repeated plunging dives near the nest to advertise ownership of a territory or as a part of courtship. Plumage patterns and other physical characteristics, such as the bare skin on the face of the crested caracara (Caracara cheriway) that changes from orange to yellow in excitement, may serve as social signals of good health or prowess, or may advertise occupation of a territory.

Sight is the most important sense used for hunting. Falconids have exceptional eyesight, which they use for catching fast-moving prey. Sound is also used by some forest-dwelling species, many of which have a ruff of stiff feathers around the face that help to capture sound. ("Falcons and Caracaras (Falconidae)", 2002; Snyder, 2001; White, Olsen, and Kiff, 1994)

Most falconids are carnivores, though several species are scavengers and some caracaras include plant matter in their diet. As a whole, falconids eat a wide variety of prey. While some species are more specialized than others, most will opportunistically take a variety prey. Prey items include mammals (from mice to lambs), adult and nestling birds, snakes, lizards, turtles, frogs, fish, crayfish, adult and larval insects, wasp and bee nests, fruit, carrion and dung. Most falconids catch prey from soaring flight or by darting from a concealed perch, but a variety of other hunting methods are also employed. Pairs of Aplomado falcons (Falco femoralis) hunt cooperatively to flush and catch small birds. Some caracaras walk or run over the ground to scatter and catch insects. Yellow-headed caracaras (Milvago chimachima) pick ticks from the backs of cattle, among other hunting methods. Kleptoparasitism (stealing food from other birds) is a common behavior among falconids, who steal from gulls, pelicans and other raptors. Food caching is also quite common. ("Falcons and Caracaras (Falconidae)", 2002; White, Olsen, and Kiff, 1994)

Falconids do not have many natural predators. However, colonial-nesting and foraging species are known to cooperatively defend against potential predators, which include eagles. (White, Olsen, and Kiff, 1994)

As predators, falconids impact populations of their prey on a local scale. Falconids are also host to feather lice.

Black caracaras (Daptrius ater) have a mutualistic relationship with tapirs. The caracaras eat ticks off of the tapirs, which seem to solicit the caracaras by calling and laying down to have the ticks removed. ("Falcons and Caracaras (Falconidae)", 2002; Snyder, 2001; White, Olsen, and Kiff, 1994)

Falconids occasionally depredate livestock, poultry, pigeons and native game birds, leading to conflict with humans. ("Falcons and Caracaras (Falconidae)", 2002; White, Olsen, and Kiff, 1994)

Falcons have been serving falconers for as long as 2000 years. Falconry continues to be popular today, with as many as 20,000 practitioners worldwide. ("Falcons and Caracaras (Falconidae)", 2002; White, Olsen, and Kiff, 1994)

The most significant threat facing falconid populations today is habitat destruction due to intensified human land use, such as logging and clearing of forests. While habitat changes such as forest clearing favor some falconid species, other species that depend on intact forest habitat are declining as a result of development. Many falconid species suffered population declines during the 1960’s and 70’s as the result of poisoning from widespread organochlorine pesticide use. While use of organochlorine pesticides has been eliminated in many countries, it continues in some lesser-developed countries. Local threats to falconid populations include introduced predators, secondary poisoning (from poisons meant for other species), collision with man-made objects such as cars, windows and windmills, bird and egg collection for trade, and electrocution on power lines.

A few species of falconids have successfully adapted to urban landscapes. For example, peregrine falcons are able to nest on buildings, bridges and overpasses, and are able to achieve similar, and sometimes even higher reproductive success compared to pairs nesting in more natural landscapes.

One species of falconid has gone extinct in recorded history. Guadeloupe caracaras (Polyborus plancus lotosus) went extinct around 1600. Today, the IUCN lists 4 species as vulnerable and 6 species as near threatened. All species of Falconids are listed under CITES Appendix I or Appendix II. ("Falcons and Caracaras (Falconidae)", 2002; "UNEP-WCMC Species Database: CITES-Listed Species", 2003; Cade et al., 1996; IUCN, 2003; Kemp and Newton, 2003; White, Olsen, and Kiff, 1994)