Falconidae

(vertebrate zoology) The falcons, a family consisting of long-winged predacious birds in the order Falconiformes.

(Falconidae)

Class: Aves

Order: Falconiformes

Suborder: Falcones

Family: Falconidae

Thumbnail description
Small to medium-sized largely diurnal raptors with strong feet, usually pointed wings, and sharply curved beaks; from scavengers to among the swiftest and, for their size, most powerful of avian predators

Size
5.5–25.6 in (14–65 cm); 0.06–4.6 lb (28–2,100 g)

Number of genera, species
10 genera; about 62 species

Habitat
Most habitats, from treeless desert and tundra to dry forest and rainforest, featureless plains to rugged gorges and escarpments

Conservation status
Vulnerable: 4 species; Near Threatened: 6 species; one subspecies Extinct

Distribution
Worldwide, except the Antarctic

Evolution and systematics

The relationship of falconids to other birds has long been unclear. Their similarity to the accipitrids (family Accipitridae, hawks and eagles) is obvious, and it has been suggested that they have morphological and anatomical links with the owls. Yet molecular evidence suggests that in both cases the resemblance is convergent; that they have evolved to look and behave in a similar fashion because of their similar lifestyles. One classification, based on DNA hybridization, groups them within the Ciconiiformes (herons, storks, and ibises). Nevertheless, in most modern classifications they are still placed with the accipitrids in the order Falconiformes.

There is no good fossil evidence to suggest where the family might have originated geographically. Africa now has the greatest diversity of falcons, but that does not necessarily reflect their past distribution or give clues about where they might have arisen. Contemporary caracaras and forest falcons (Polyborinae) are South and Central American, and there is no indication the subfamily was ever otherwise, so it seems reasonable to suggest they arose in the neotropics.

The earliest fossil attributed to the family was found in England and dated to 55 million years ago. Better-substantiated fossil members of the family have been reported from 36-million-year-old deposits in France. In the Americas, falconids have been identified from 23 million years ago, including a caracara-like form. The falcons, genus Falco, the largest group of falconids, are clearly closely related and are thought to have undergone rapid radiation and expansion early in the Pleistocene (about 1.85 million years ago), when the grasslands opened up.

Within the family, division into the two subfamilies is well supported but there is much argument over relationships within each. Nevertheless, each major region has its group of similar, presumably closely related forms (gray falcon [Falco hypoleucos], black falcon [F. subniger], brown falcon [F. berigora] and New Zealand falcon [F. novaeseelandiae] in Australasia) and there are a few groups of more widespread sister species (the desert falcons, kestrels, peregrines, and hobbies).

Physical characteristics

Falconids are readily recognizable as birds of prey and are likely to be confused only with the other family of diurnal raptors, the Accipitridae. Both have a fleshy cere atop a strong hooked beak, and a strong hallux (hind toe) that opposes three forward toes. Both families capture animals with their feet and, unlike most bird species, females are larger than males. The difference between the sexes is greatest in bird-eaters (female around 150% of male weight), intermediate in mammal-eaters, and least in insect-eaters and scavengers (females marginally heavier).

Differences between the families include several anatomical features, such as the structure of the syrinx, the fact that falconids kill with the beak or by the blow when they strike (accipitrids squeeze with their feet), and eggs that have reddish translucence when held up to the light (accipitrid eggs are bluish or greenish).

Most falconids have strong needle-sharp talons. The exception is the caracaras, which have heavy but flatter talons for their more terrestrial, vulture-like lifestyle. Other structures also vary with lifestyle, form reflecting function. Hence, toes of bird-catching species are long and slender, mammal eaters have thicker toes, and snake eaters the shortest and thickest. Beaks also vary with prey: short and robust in most species, particularly deep in species that take large prey; longer and less powerful in carrion eaters. Fast aerial falconids of open country or those that migrate tend to have the longest, most pointed wings. Slower species tend to have slightly broader wings. Forest-dwelling species have short rounded wings and a long tail that gives them maneuverability in tight spaces.

Plumages tend to be fairly cryptic: shades of brown, black, and gray or white, often mottled or streaked. The caracaras, which tend to be mostly scroungers with no need for camouflage, are more colorful and some have raven-like, glossy black feathers with a green sheen. Most species have yellow soft parts (cere, narrow eye-ring, legs, and feet), occasionally gray or red. Caracaras and forest falcons are distinguished by obvious areas of featherless bright red or yellow skin around the face, more extensive in the more scavenging species.

The family is noted for its powers of sight, with an ability to detect the smallest movement at great distance. Most have rather large brown eyes; those living in dimly lit habitats or that regularly hunt into the evening tend to have the largest eyes.

Distribution

Except for the Antarctic and parts of the far high Arctic, the falcons alone are distributed worldwide. The remaining Falconinae, the falconets, are mainly tropical Spiziapteryx (1 South American species), Polihierax (1 African species; 1 Indian), and Microhierax (5 Asian species).

All 16 species of Polyborinae are neotropical, mainly South American, and do not venture beyond that region. These include caracaras Daptrius (2 species), Phalcoboenus (4), Polyborus(1), Milvago (2), laughing falcon Herpetotheres (1), and forest falcons Micrastur (6).

Of the Falconinae, several falcons migrate from one region to another (most from Eurasia to Africa; none to Australia).

Among breeding grounds, the species are distributed as follows, and some occur in more than one region: Australasia (8 falcons), African region (1 pygmy falcon Polihierax, 14 falcons), Central and South America (3 falcons), North America (9 falcons), and Eurasia (6 falconets, 11 falcons).

Individual species vary widely in the extent of their distribution. The peregrine falcon (Falco peregrinus, meaning the wanderer) is the most widespread of all, occurring almost everywhere habitat is suitable, with a few notable gaps such as New Zealand. The Seychelles (F. araea) and Mauritius (F. punctatus) kestrels are probably the most restricted in distribution, confined to some tiny islands of the Seychelles and Mauritius, Indian Ocean. The crested caracara (Polyborus plancus), found throughout South and Central America, has the most extensive range of the Polyborinae. The striated caracara (Phalcoboenus australis) and plumbeous forest falcon (Micrastur plumbeous) are very localized. Perhaps not surprisingly, all species with very limited distributions are listed as being threatened with extinction.

Several species extended their distribution in historical times because extra habitat was created for them or they adapted to disturbed habitats. One example is the Australian kestrel (F. cenchroides), which has established populations on Christmas Island, Indian Ocean, and Norfolk Island, southwest Pacific Ocean. The kestrel self-colonized both islands; the former by hitching a ride on warships operating in the area during World War II, the latter after the rainforested island was turned to farmland.

One species was purposely introduced and became established: the chimango caracara (Milvago chimango), endemic to southern South America, was translocated to Easter Island, South Pacific, in 1928 and is now common.

Habitat

As a group, the falconids occur in most major habitats around the world. They reach their greatest diversity near the tropics and only two species are found in the high Arctic (gyrfalcon F. rusticolis, peregrine falcon). Many species are quite adaptable and for them the structure of the habitat is more important than its individual components. For these species, habitat disturbance may not be important provided prey and nest sites are still available. For example, conversion of forest and woodland to farmland appears to have favored the Australian kestrel, but recent agricultural intensification has rendered some areas unsuitable again. Another example is the use of city canyons by peregrine falcons and several species of kestrel; cities and suburbs can offer nest sites, abundant prey (pigeons, starlings, rats, insects), and refuge from persecution.

Other species are more specialized. For example, several forest falcons need large tracts of more-or-less intact forest. Eleanora's falcon (F. eleanorae) nests on a few small quiet islands and islets, pockmarked with holes and ledges and sited on the migratory routes of small birds in the Mediterranean. In the nonbreeding season the population migrates to a very different habitat in the open woodlands and forests of Madagascar.

Typically, forest falcons and falconets require forest and forest clearings and edges. In contrast, falcons and caracaras favor open country, from grasslands to open woodlands and scrub. As always there are exceptions; the bat falcon (F. rufigularis) depends on forest edge, and the Seychelles kestrel lives in dense secondary forest.

In the nonbreeding season many species, such as Eleanora's falcon and several from high latitudes in the Northern Hemisphere, make drastic habitat changes. Annually, the entire population leaves breeding grounds made barren by the winter desertion of small birds or by snowfalls to fly across the globe to more productive zones. Other species make less drastic, more unpredictable shifts in distribution, such as local movements down from the mountains to winter in milder coastal areas. The African pygmy falcon (Polihierax semi-torquatus) leaves more arid parts of its range when the season is particularly dry. In some species there may be no shift in mild winters, or only part of the population may leave to winter elsewhere. In many species, such as several kestrels, females are most likely to depart the breeding grounds for the winter; males will stay if they can support themselves.

Behavior

Typically, falconids are active by day, but several species hunt crepuscularly. For example, the Eurasian hobby (F. sub-buteo) chases moths after dusk, and peregrine falcons hunt shearwaters as they return to their holes well after dark. At night they usually roost at a regular roost, sheltered from the prevailing elements and safe from predators. Even on migration, the same roosts are often used year after year.

Some species are resident, others are migratory or partially migratory (in areas where winter is harsh, part of the population migrates). Distances traveled range from 6,000–12,000 mi (10,000–20,000 km) (Arctic peregrine falcons) down to very local shifts (e.g., Australian peregrine falcons), both to areas where prey is more available. One of the most dramatic examples is the movement of several falcons from Eurasia and the Mediterranean to Africa and Madagascar, to feed on vast swarms of termites and ants that arise during the wet season. Some species gather in flocks and move en masse (red-footed falcon F. vespertinus), others find their way individually. Juveniles of most species disperse after their post-fledgling dependency, except for juveniles of the red-throated caracara, that may join the communal group. In all species studied, juveniles are more dispersive than adults, and females tend to depart earlier and move farther than males.

Although falcons are typically viewed as solitary creatures, many species are gregarious and may flock together to feed, roost, breed, or migrate. Some flock opportunistically (many kestrels), others live in cooperative groups as a way of life (red-throated caracara Daptrius americanus). Still others live in loose groups but don't directly assist each other (Eleanora's falcon). At the other end of the spectrum are purely solitary species that are highly territorial year-round (collared falconet Microhierax caerulescens).

Falconids have rather harsh voices, at least for longer-distance communication. For more intimate contact they make softer sounds. Forest falcons and laughing falcons call at dawn (and again at dusk), presumably to advertise that they are still present on their territory in the dense forest. Caracaras are also rather vocal, particularly when annoyed over food or other territorial disputes, throwing their heads back to release the far-carrying calls for which they are named. By contrast, falcons can be rather silent, mainly heard when humans disturb a nest and the falcons call in defense (usually a strident kak kak kak kak that is higher pitched in smaller species).

Feeding ecology and diet

Feeding ecology is a better-known aspect of falconoid ecology, mainly because they eat large prey and produce pellets (wads of indigestible parts of the prey—fur, feathers, scales, bone—that are regurgitated once a day or so) that can be analyzed for the prey they contain. Pellets build up under nests and roosts and make interesting study.

Falconids are predatory meat eaters, yet some also scavenge and the caracaras eat some vegetable matter. Several, especially the more aggressive species (black falcons F. subniger, and caracaras), are not above stealing prey from other raptors, herons, and others. Some species are specialized; for example, the peregrine feeds mainly on birds and the laughing falcon on snakes, but both take a variety of species in those prey groups. The gyrfalcon takes ground-dwelling creatures such as medium-sized mammals and terrestrial birds. Other species spread their diet over a range of prey groups. Caracaras can kill prey as large as lambs and capture birds on the wing, but mostly they scrounge for carrion (especially its maggots) and horse dung, and take easier prey such as earthworms, maggots, lizards, insects, nestling birds, frogs, and fish. Forest caracaras (Daptrius) eat fruit, and wasp and bee nests, for which they seem to have a repellant that protects them from stings from the angry insects. The black caracara (D. ater) picks ticks off tapirs, which appear to solicit the caracaras by calling and then lying down to have the ticks removed. Many species hawk moths in the evening and insects on the wing, especially when the insects swarm, such as after rain and around water. In the breeding season most species concentrate on live prey. Juveniles tend to capture easier prey (such as insects) than do adults.

Hunting methods are as varied as the diet. Bird-catching falcons (even diminutive falconets) are the most spectacular hunters, sometimes catching prey as large as themselves at breathtaking speed, either in a direct tail chase or by diving from height to strike with great force. Other species capture prey on the ground or as it flushes. Most kestrels hover (giving them a fixed aerial vantage point from which to spot and drop onto prey) or swoop down from a perch. Some longerlegged species run over the ground after insects.

Falcons tend to hunt in the open, by sight. Forest falcons make greater use of sound to locate prey in the dim dense forest, and have a circle of stiff feathers around the ear openings to funnel sound to the ears. All species use the element of surprise to improve their success rate.

Most species hunt alone, occasionally as cooperative pairs (several falcons), and a few forage cooperatively in groups (red-throated caracara). Several species use herds, tractors, fires, cars, and other birds to flush prey. Most if not all falcons cache a little prey in excess of their immediate needs, placing it in a rock crevice or under a grass tussock for later retrieval.

Reproductive biology

Most falconids breed once a year in a traditional breeding territory. Territories range from a few square yards (meters) for colonial species like the lesser kestrel (Falco naumanni) and Eleanora's falcon, to 400 mi² (1,000 m²) for the solitary nesting gyrfalcon. Spacing between pairs depends on food and nest availability. Typically falconids are monogamous, nesting as solitary faithful pairs. Yet many variations in breeding arrangements found in other birds are present in the family. About 10% of falconids are colonial or semicolonial and nest in loose groups. The red-throated caracara has a more cooperative approach to group living; only the alpha pair breeds and it is assisted in feeding and protection by other group members. Some peregrine falcon pairs in France had an extra female who appeared to help with feeding, leading to greater breeding success at assisted nests. Pygmy falcons are sometimes polyandrous, with more than one male attending the nest and presumably having a chance to father young.

Most species have courtship rituals involving fancy flying and increased calling. Except for the caracaras, falconids do not build nests. Rather they use a tree hole or cliff cavity, an open stick or enclosed woven nest of another species, an epiphyte, or some other suitable situation. Caracaras build an untidy nest of sticks or dried grass, sometimes lined with wool or grass.

Caracaras, forest falcons, and many of the falcons lay two to three red-brown blotched buff eggs. The laughing falcon lays a single dark egg; the falconets and some species that nest in harsher environments lay three to four or more eggs. Some falcons (gyrfalcon, many kestrels) lay a much larger clutch when conditions are good than when they are poor; other species are more conservative in the size of their clutch (brown falcon, peregrine falcon, island kestrels). Widespread species have smaller clutches in milder parts of their range.

Typically, there is a division of roles: the female does most of the incubation and the male catches prey for her and the chicks, at least for the first part of the nestling period when she is brooding. Incubation is quite fixed for individual species and ranges from about 28 days for smaller species to 35 days for the gyrfalcon. The length of the nestling period is also related to size, with smaller species (falconets and small falcons) taking four weeks, larger species seven or eight weeks (gyrfalcons and caracaras). The nestlings grow rapidly and at fledgling are as heavy as the adults but with flight feathers (wing and tail) not quite fully grown. Fledglings are dependent on adults for variable periods, seemingly longer in species that hunt difficult or scarce prey.

Conservation status

Falcons and caracaras have a long history of persecution for their perceived impact on livestock. Particularly in the 1960s and 1970s, organochlorine pesticides (DDT, dieldrin, and others) had a very real impact on eggshell thickness and the mortality of some species, leading to massive population declines. Yet the group's remarkable resilience is illustrated by the fact that no species are currently listed as Endangered or Critically Endangered, the two highest-risk categories used by the World Conservation Union (IUCN).

Only one falconid has become extinct in historical times: the Guadeloupe caracara (Polyborus plancus lutosus) of Isla Guadeloupe, Mexico. It is generally regarded as a subspecies of the crested caracara (P. plancus), which is widespread on the Central and South American mainlands, but some taxonomists consider it a full species. Regardless, settlers persecuted the caracara and it has not been seen since 1900. Its demise must have been accelerated by the denuding of the island's dense vegetation by goats.

The main threat for falconids in general is widespread habitat destruction by logging, clearing and burning of forests and woodlands, and intensifying land-use by humans for agriculture, grazing, subsistence hunting, or housing. Local impacts include introduced predators, pesticides, and trade in birds and eggs. Threats to survival of the IUCN-listed species are typical of those facing most falconids.

Four species, the Plumbeus forest falcon and three kestrels, are listed as Vulnerable; that is, they face extinction in the medium-term future if factors causing their vulnerability are not reversed or held at bay. All three kestrels—Seychelles, Mauritius, and lesser kestrels—are found in the African region. The lesser kestrel is a winter migrant to the region, South Africa in particular. In 2000 its world population was estimated to have declined by about 50% in the past 50 years, recovering to 80% of former numbers in the past decade. Deforestation and urbanization of its extensive breeding grounds in western Europe and elsewhere, and intensification of agriculture in its breeding and wintering grounds are believed to be major causes of decline. The other two kestrels are confined to islands where their forest habitat is decimated and introduced predators raid their nests. Conservation actions such as restoring and predator-proofing nest sites are helping all three species. As a result of a captive breeding-forrelease program and management in the wild, the Mauritius kestrel was recently down-listed from Endangered because its population has undergone a spectacular recovery, from about four wild birds in the 1970s to more than 500 in 2000.

Another six species are considered Near Threatened. The striated caracara occurs in low numbers on islands and islets off southern Argentina and Chile, including the Falklands where it was persecuted for its occasional attacks on weak or stranded sheep. At present it seems to be free of major threats but remains vulnerable because of its small population. The five remaining species are not well known but are presumed to have a small total population. The two falconets are Asian in distribution, where habitat clearing is a major problem. The white-rumped falcon (Polihierax insignis) was once widespread and common in the grasslands and deciduous forests of Thailand, Laos, Cambodia, and Vietnam, and may still survive in extensive areas that remain uncleared. The white-fronted falconet (Microhierax latifrons) has a very restricted distribution centered on Sabah, Malaysia; an ability to survive in disturbed habitats may allow it to persist. Past habitat clearance, persecution by farmers and pigeon and poultry keepers, and egg destruction by possums introduced from Australia have caused concern for the New Zealand falcon, but population trends are unknown. The gray falcon is thinly scattered across vast spaces of arid and semiarid Australia and, while it may have suffered some small past contraction in range from habitat loss to grazing by livestock, its population is thought to be stable. Similarly, the taita falcon (F. fasciinucha) occurs in naturally low densities in scattered gorges and escarpments from Ethiopia to South Africa, and no major threats are apparent.

Regional conservation initiatives have had some success; for example, reserves such as the Snake River Bird of Prey Conservation Area in Idaho. There, 800 pairs of 15 species nest and another nine use the park to winter or stop over on migration. Guarding nests at risk from egg collectors and falconers, and fostering nestlings into safer nests bolsters populations. In recent decades, education and promotion has generally increased tolerance of predatory birds and appreciation of their place in nature. Many falconids, such as the peregrine falcon, bat falcon (F. rufigularis), merlin F. columbarius), and various kestrels have moved into suburbs and cities where they hunt in the urban spaces and city skies, and nest in parklands and on buildings.

Significance to humans

Falconids have had a long association with people, and tend to elicit a strong response as friend or foe. They are much admired for their hunting prowess, flying skills, and keen sight, and appear as icons and in the legends and folklore of many cultures. In ancient Egypt, Horus the falcon god was ubiquitous, and as a hieroglyph, Horus represented the king. Falcons (Lanner F. biarmicus, Barbary falcon F. peregrinus pelegrinoides, a desert race of the peregrine, common F. tinnunculus and perhaps lesser kestrels) were buried in tombs, often mummified. At about the same time (2000 B.C.) or earlier, falcons were used to capture meat for humans. The first known falconry was practiced in Asia, from which it spread. It was most popular in Europe in medieval times (twelfth century), when kings, merchants, and even nuns kept trained falcons. Some of the jargon, such as haggard (a wild-caught adult falcon), has become part of everyday language. Today falconry is still popular where it is not outlawed by wildlife-protection legislation, particularly in the Middle East. Falconids are still significant to some indigenous peoples as totems and in legend. For similar reasons, they appear as symbols of strength, courage, or speed on crests and in logos and product names.

Paradoxically, often falconids are hated because of their depredations on livestock, poultry, pigeons, and even native birds. This is most often a case of misunderstanding of their role in nature and an exaggeration of their impact.

Because pesticide use caused it to vanish from vast areas of its natural range, the peregrine falcon became a flagship of the conservation movement. A concerted effort restored the peregrine and other affected species to much of their range. Although many falconids have adapted to altered environments and human activities, they remain charismatic symbols of a natural world.

Species accounts

Resources

BirdLife International. Threatened Birds of the World. Barcelona and Cambridge: Lynx Edicions and BirdLife International, 2000.

Brown, L. H., E. K. Urban, and K. Newman. The Birds of Africa. Vol. 1. London: Academic Press, 1982.

Cade, T. J. Falcons of the World. London: Collins, 1982.

Cade, T. J. "Progress in Translocation of Diurnal Raptors." In Raptors at Risk, ed. R. D. Chancellor and B.-U. Meyburg. Berlin and London: World Working Group on Birds of Prey and Hancock House, 2000.

Clum, N. J., and T. J. Cade. "Gyrfalcon Falco rusticolus." Birds of North America. No. 114. 1995.

Cramp, S., ed. The Birds of the Western Palearctic. Vol. II, Hawks to Bustards. Oxford: Oxford University Press, 1980. del Hoyo, J. A., A. Elliot, and J. Sargatal, eds. Handbook of the Birds of the World. Vol. 2. New World Vultures to Guineafowl. Barcelona: Lynx Edicions, 2000.

Eastham, C. P., J. L. Quinn, and N. C. Fox. "Saker Falco cherrug and Peregrine Falco peregrinus Falcons in Asia: Determining Migration Routes and Trapping Pressure." In Raptors at Risk, ed. R. D. Chancellor and B.-U. Meyburg. Berlin and London: World Working Group on Birds of Prey and Hancock House, 2000.

Fox, N. Understanding the Bird of Prey. Surrey: Hancock House, 1995.

Love, O. P., and D. M. Bird. "Raptors in Urban Landscapes: A Review and Future Concerns." Raptors at Risk, ed. R. D. Chancellor and B.-U. Meyburg. Berlin and London: World Working Group on Birds of Prey and Hancock House, 2000.

Mindell, D. P. Avian Molecular Evolution and Systematics. San Diego: Academic Press, 1997.

Newton, I., and P. Olsen, eds. Birds of Prey. London: Merehurst, 1990.

Olsen, P. Australian Birds of Prey. Sydney and Baltimore: New South Wales Press and Johns Hopkins, 1995.

Sibley, C. G., and J. E. Ahlquist. Phylogeny and Classification of Birds. New Haven: Yale University Press, 1990.

Wink, M., and P. Heidrich. "Molecular Evolution and Ssystematics of the Owls." In Owls: A Guide to Owls of the World, ed. C. Konig, F. Weick, and J.-H. Becking. Sussex: Pica, 1999.

The Hawk and Owl Trust. 11 St Marys Close, Abbotskerswell, Newton Abbot, Devon TQ12 5QF United Kingdom. Phone: +44 (0)1626 334864. Fax: +44 (0)1626 334864. E-mail: hawkandowl@aol.com Web site:

World Center for Birds of Prey, The Peregrine Fund.. 566 West Flying Hawk Lane, Boise, Idaho 83709 USA. Phone: (208) 362-3716. Fax: (208) 362-2376. E-mail: tpf@peregrinefund.org Web site:

World Working Group on Birds of Prey and Owls. P.O. Box 52, Towcester, NN12 7ZW United Kingdom. Phone: +44 1 604 862 331. Fax: +44 1 604 862 331. E-mail: WWGBP@aol.com Web site:

[Article by: Penny Olsen, PhD]

The noun has one meaning:

Meaning #1: a family of birds of the order Falconiformes
  Synonym: family Falconidae

Falcons and caracaras
Brown Falcon Falco berigora
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Falconiformes
Family:	Falconidae Vigors, 1824
Subfamilies
Falconinae Polyborinae

The falcons and caracaras are around 60 species of diurnal birds of prey that comprise the family Falconidae. The family is divided into two subfamiles, Polyborinae, which includes the caracaras and forest falcons, and Falconinae, the falcons, kestrels and falconets.

Contents 1 Description 2 Distribution and habitat 3 Behaviour 3.1 Diet and feeding 3.2 Breeding 4 Relations with humans 5 Classification problems 5.1 Genera in taxonomic order 5.2 Fossil genera 6 External links 7 Footnotes 8 References

Description

Falcons and caracaras are small to medium sized birds of prey, ranging in size from the Black-thighed Falconet, which can weight as little as 35 grams (1.2 oz), to the Gyrfalcon, which can weigh as much as 1,735 grams (61.2 oz). They have strongly hooked bills, sharply curved talons and excellent eyesight. The plumage is usually composed of browns, whites, chestnut, black and grey, often with barring of patterning. There is little difference n the plumage of males and females, although a few species have some sexual dimorphism in boldness of plumage.

They differ from other Falconiformes in killing with their beaks instead of their feet. They have a "tooth" on the side of their beak for the purpose.

Distribution and habitat

The family has a cosmopolitan distribution across the world, absent only from the densest forest of central Africa, some remote oceanic islands, the high Arctic and Antarctica. Some species have exceptionally wide ranges, particularly the cosmopolitan Peregrine Falcon, which ranges from Greenland to Fiji and has the widest natural breeding distribution of any bird. Other species have more restricted distributions, particularly island endemics like the Mauritius Kestrel. Most habitat types are occupied, from tundra to rainforest and deserts, although they are generally more birds of open country and even forest species tend to prefer broken forest and forest edges. Some species, mostly in the genus Falco, are fully migratory, with some species in Eurasia and wintering entirely in Africa, other species may be partly migratory. The Amur Falcon has one of the longest migrations, moving from East Asia to southern Africa.^[1]

Behaviour

Diet and feeding

The Laughing Falcon is a snake-eating specialist

.

Falcons and caracaras are carnivores, feeding on birds, small mammals, reptiles, insects and carrion. In popular imagination the falconids are fast flying predators, and while this is true of the genus Falco and some falconets other species, particularly the caracaras are more sedentary in their feeding. The forest falcons of the Neotropics are generalist forest hunters. Several species, particularly the true falcons, will stash food supplies in caches.^[2] They are solitary hunters and pairs guard territories, although they may form large flocks during migration. Some species are specialists, the Laughing Falcon specialises in snakes, others are more generalist.

Breeding

The Red-footed Falcon is unusual in being a colonial breeding falcon.

The falcons and caracaras are generally solitary breeders, although around 10% of species are colonial, for example the Red-footed Falcon.^[3] They are monogamous, although some caracaras may also employ alloparenting stratergies, where younger birds help adults (usually their parents) in raising the next brood of chicks. Nests are generally not built (except by the caracaras), but are co opted from other birds, for example African Pygmy-falcons nest in the nests of weavers, or on the ledges on cliffs. Around 2-4 eggs are laid, and mostly incubated by the female. Incubation times vary from species to species and are correlated with body size, lasting 28 days in smaller species and up to 35 days in larger species. Chicks fledge after 28-49 days, again varying with size.

Relations with humans

Falcons and caracaras have a complicated relationship with humans. In ancient Egypt they were deified in the form of Horus, the Sky and Sun God, and was the ancestor of the Pharaohs. Caracaras also formed part of the legends of the Aztecs, and are today the national emblems of Mexico. Falcons were important in the (formerly often royal) sport of falconry. They have also been persecuted for their predation on game and farm animals, and that persecution has led to the extinction of at least one species, the Guadalupe Caracara. Several insular species have declined dramatically, none more so than the Mauritius Kestrel, which at one time numbered no more than four birds. Around four species of falcon are considered vulnerable to extinction by the IUCN, with one species, the Saker Falcon, listed as endangered.

Classification problems

Traditionally, all the raptors are grouped into 4 families in this single order. However, in Europe, it has become common to split the order into two: the falcons and caracaras remain in the order Falconiformes (about 60 species in 4 groups), and the remaining 220-odd species (including the Accipitridae – eagles, hawks, and many others) are put in the separate order Accipitriformes. A prehistoric family known only from fossils are the Horusornithidae.

The idea that Falconiformes should be divided into many orders comes from the suggestion that the order may not share a single lineage that is exclusive of other birds. The most controversial but also most well-supported suggestion is that Cathartidae are not Falconiformes but are related to the storks, in the separate order Ciconiiformes. However, morphological evidence supports the common ancestry of the Falconiformes, and the Strigiformes may be very close to the Falconiformes as well.

The American Ornithologists' Union reintegrated the New World vultures (family Cathartidae) into Falconiformes in 2007^{[verification needed]}. This goes against the influential Sibley-Ahlquist taxonomy, in which all the raptors are placed into Ciconiiformes, but the Cathartids are considered to be outside the lineage that includes other raptors. While the latter is apparently correct, the "Ciconiiformes" sensu Sibley & Ahlquist are a paraphyletic, artificial assemblage and one of the weakest point of their classification scheme.

Genera in taxonomic order

The Yellow-headed Caracara is a species in the genus Milvago.

Family: Falconidae

• Genus Daptrius – Black Caracara
• Genus Ibycter – Red-throated Caracara (sometimes included in Daptrius)
• Genus Phalcoboenus (4 species)
• Genus Caracara – crested caracaras (2 living species, 1 extinct)
• Genus Milvago – brown caracaras (2 species)
• Genus Herpetotheres – Laughing Falcon
• Genus Micrastur – forest falcons (7 species)
• Genus Spiziapteryx – Spot-winged Falconet
• Genus Polihierax – pygmy-falcons (2 species, includes Neohierax)
• Genus Microhierax – typical falconets (5 species)
• Genus Falco – true falcons, hobbies and kestrels (around 37 species)

Fossil genera

• Parvulivenator (Early Eocene of England)
• Stintonornis (London Clay Early Eocene of England)
• Badiostes (Santa Cruz Early Miocene of Patagonia, Argentina)
• Falconidae gen. et sp. indet. (Early Miocene of Chubut, Argentina)
• Falconidae gen. et sp. indet. (Pinturas Early/Middle Miocene of Argentina)
• Pediohierax (Middle Miocene of Nebraska, USA) – formerly Falco ramenta
• Falconidae gen. et sp. indet. (Cerro Bandera Late Miocene of Neuquén, Argentina)^[4]
• "Sushkinia" pliocaena (Early Pliocene of Pavlodar, Kazakhstan) – belongs in Falco?

External links

Wikimedia Commons has media related to: Falconidae

• Falconidae videos, photos and sounds on the Internet Bird Collection
• Falconidae sounds in the xeno canto collection

Footnotes

1. ^ Tordoff, Andrew (2002). "Raptor migration at Hoang Lien Nature Reserve, northern Vietnam" (pdf). Forktail 18: 45-48. 
2. ^ Collopy M.W. (1977) "Food Caching by Female American Kestrels in Winter" Condor 79 (1): 63-68
3. ^ Ille, R.; Hoi, H.; Grinschgl, F. & F. Zink (2002) "Paternity assurance in two species of colonially breeding falcon: the kestrel Falco tinnunculus and the red-footed falcon Falco vespertinus" Etologica 10 11-15
4. ^ PVPH 465: a phalanx 1 of the middle toe. A caracara? Possibly belongs in extant genus.(Kramarz et al. 2005)

References

• Kramarz, Alejandro: Garrido, Alberto; Forasiepi, Analía; Bond, Mariano & Tambussi, Claudia (2005): Estratigrafía y vertebrados (Aves y Mammalia) de la Formación Cerro Bandera, Mioceno Temprano de la Provincia del Neuquén, Argentina. Revista geológica de Chile 32(2): 273-291. HTML fulltext

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