Ferruginous Hawk
Encyclopedia
The Ferruginous Hawk Buteo regalis (Latin, royal hawk), is a large bird of prey
Bird of prey
Birds of prey are birds that hunt for food primarily on the wing, using their keen senses, especially vision. They are defined as birds that primarily hunt vertebrates, including other birds. Their talons and beaks tend to be relatively large, powerful and adapted for tearing and/or piercing flesh....

. It is not a true hawk
Accipiter
The genus Accipiter is a group of birds of prey in the family Accipitridae, many of which are named as goshawks and sparrowhawks. They can be anatomically distinguished from their relatives by the lack of a procoracoid foramen. Two small and aberrant species usually placed here do possess a large...

 like sparrowhawks or goshawks, but rather belongs to the broad-winged buteo hawks
Buteo
Buteo is a genus of medium to fairly large, wide-ranging raptors with a robust body and broad wings. In the Old World, members of this genus are called "buzzards", but "hawk" is used in North America...

, known as "buzzard
Buzzard
A buzzard is one of several large birds, but there are a number of meanings as detailed below.-Old World:In the Old World Buzzard can mean:* One of several medium-sized, wide-ranging raptors with a robust body and broad wings....

s" in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

. An old colloquial name is "Ferrugineous Rough-leg", due to its similarity to the closely related Rough-legged Hawk (B. lagopus).

This species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 is a large, broad-winged hawk of the open, arid grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...

s, prairie
Prairie
Prairies are considered part of the temperate grasslands, savannas, and shrublands biome by ecologists, based on similar temperate climates, moderate rainfall, and grasses, herbs, and shrubs, rather than trees, as the dominant vegetation type...

 and shrub steppe
Steppe
In physical geography, steppe is an ecoregion, in the montane grasslands and shrublands and temperate grasslands, savannas, and shrublands biomes, characterized by grassland plains without trees apart from those near rivers and lakes...

 country; it is endemic to the interior parts of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. It is used as a falconry
Falconry
Falconry is "the taking of wild quarry in its natural state and habitat by means of a trained raptor". There are two traditional terms used to describe a person involved in falconry: a falconer flies a falcon; an austringer flies a hawk or an eagle...

 bird in its native range.

Description

This is the largest of the Buteo
Buteo
Buteo is a genus of medium to fairly large, wide-ranging raptors with a robust body and broad wings. In the Old World, members of this genus are called "buzzards", but "hawk" is used in North America...

s
and is often mistaken for an eagle
Eagle
Eagles are members of the bird family Accipitridae, and belong to several genera which are not necessarily closely related to each other. Most of the more than 60 species occur in Eurasia and Africa. Outside this area, just two species can be found in the United States and Canada, nine more in...

 due to its size, proportions, and behavior. As with all birds of prey, the female is larger than the male, but there is some overlap between small females and large males in the range of measurements. Length ranges from 20 to 27 in (50.8 to 68.6 cm) with an average of 23 inches (58.4 cm), wingspan from 48 to 60 in (121.9 to 152.4 cm) with an average of 56 inches (142.2 cm), and weight from 2.1 to 5 lb (952.5 to 2,268 g).

Adults have long broad wings and a broad gray, rusty, or white tail. The legs are feathered to the talons, like the Rough-legged Hawk. There are two color forms:
  • Light morph birds are rusty brown on the upper parts and pale on the head, neck, and underparts with rust on the legs and some rust marking on the underwing. The upper wings are grey. The "Ferruginous" name refers to the rusty color of the light-morph birds.
  • Dark-morph birds are dark brown on both upperparts and underparts with light areas on the upper and lower wings.


There are no subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

.

Voice

The voice
Bird song
Bird vocalization includes both bird calls and bird songs. In non-technical use, bird songs are the bird sounds that are melodious to the human ear. In ornithology and birding, songs are distinguished by function from calls.-Definition:The distinction between songs and calls is based upon...

 is not well-described in literature
Literature
Literature is the art of written works, and is not bound to published sources...

. Alarm calls consist of kree - a or ke - ah and harsh kaah, kaah calls, the latter resembling some vocalizations of the herring gull
American Herring Gull
The American Herring Gull or Smithsonian Gull is a large gull which breeds in North America. It is often treated as a subspecies of the European Herring Gull but is now regarded as a separate species by some authorities.Adults are white with gray back and wings, black wingtips with white spots,...

. One description referred to the "wavering" alarm call and "breathy" notes, while other authors describe screams similar to those of the Red-tailed Hawk
Red-tailed Hawk
The Red-tailed Hawk is a bird of prey, one of three species colloquially known in the United States as the "chickenhawk," though it rarely preys on standard sized chickens. It breeds throughout most of North America, from western Alaska and northern Canada to as far south as Panama and the West...

 (B. jamaicensis).

Identification

The male and female have identical markings. The main difference is size, with the female being larger. Perched birds have a white breast and body
Body
With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death...

 with dark legs. The back and wing
Wing
A wing is an appendage with a surface that produces lift for flight or propulsion through the atmosphere, or through another gaseous or liquid fluid...

s are a brownish rust color. The head is white with a dark streak extending behind the eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...

. The wing tips almost reach the tip of the tail.

The underside is primarily light colored with the dark legs forming a "V" shape. The reddish upper-back color extends to the inner wing coverts or "shoulders." The primary remiges (pinions) are dark gray with conspicuous light "windows" in the inner primaries. Three prominent light areas on the upper surface stand out as two "windows" on the outer wings and a rufous rump mark. The underwings are whitish overall with rufous markings, particularly in the patagial area. This gives a smudgy appearance to the wings, but less dark than in a Red-tailed Hawk. Dark "comma"-shaped markings are prominent at the wrist
Wrist
In human anatomy, the wrist is variously defined as 1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand;...

s. The Ferruginous Hawk is one of the only two hawks that have feathers that cover their legs down to their toes, like the Golden Eagle. The other is the Rough-legged Hawk.

In flight, these birds soar with their wings in a dihedral.

Habitat

The preferred habitat for Ferruginous Hawks are the arid
Arid
A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the growth and development of plant and animal life...

 and semiarid grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...

 regions of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

. The countryside is open, level, or rolling prairies; foothills or middle elevation plateaus largely devoid of trees; and cultivated shelterbelts or riparian corridors. Rock outcrops, shallow canyons, and gullies may characterize some habitats. These hawks avoid high elevations, forest interiors, narrow canyons, and cliff areas.

During the breeding season, the preference is for grasslands, sage
Sagebrush
Sagebrush is a common name of a number of shrubby plant species in the genus Artemisia native to western North America;Or, the sagebrush steppe ecoregion, having one or more kinds of sagebrush, bunchgrasses and others;...

, and other arid shrub country. Nesting occurs in the open areas or in trees including cottonwoods, willow
Willow
Willows, sallows, and osiers form the genus Salix, around 400 species of deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions of the Northern Hemisphere...

s, and swamp oak
Oak
An oak is a tree or shrub in the genus Quercus , of which about 600 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...

s along waterways. Cultivated fields and modified grasslands are avoided during the breeding period. The density of Ferruginous Hawks in grasslands declines in an inverse relationship to the degree of cultivation of the grasslands. However, high densities have been reported in areas where nearly 80 percent of the grassland was under cultivation.

The winter habitat is similar to that used during the summer. However, cultivated areas are not necessarily avoided, particularly when the crops are not plowed under after harvest. The standing stubble provides habitat for the small-mammal prey base needed by Ferruginous and other hawks. One requisite of the habitat is perches such as poles, lone trees, knolls, rocky outcrops or large boulders. Ferruginous Hawks nest in trees if they are available, including riparian strips, but the presence of water does not appear to be critical to them.

The Ferruginous Hawk maintains minimum distances from other nesting raptors but will nest closer than necessary, suggesting that the distance is not fixed. The "nearest neighbor" distance has varied from less than 1 miles (1.6 km) to as much as 4 miles (6.4 km) with an average of 2 miles (3.2 km). Nests facing different hunting territories are tolerated much closer than nests facing the same hunting territory. The minimum distance between nests is probably about one half mile on densely-occupied areas. Nesting densities in several studies have varied from one pair per four to 2,450 square miles (10.4 to 6,346 square km). In Alberta, on one study site, there was a stable density of one pair per four square miles (10.4 square km), on average with little deviation from this mean. In Idaho, the average home range for four pairs of Ferruginous Hawk in the Snake River area was slightly over two square miles (5.2 square km).

Behavior

The flight of the Ferruginous Hawk is active, with slow wing beats much like that of a small eagle. Soaring with the wings held in a strong dihedral has been noted, as well as gliding with the wings held flat, or in a modified dihedral. Hovering and low cruising over the ground are also used as hunting techniques. The wing beat has been described as "fluid" by some observers.

Territorial conflicts have been reported with other species, such as the Great Horned
Great Horned Owl
The Great Horned Owl, , also known as the Tiger Owl, is a large owl native to the Americas. It is an adaptable bird with a vast range and is the most widely distributed true owl in the Americas.-Description:...

 and Short-eared Owl
Short-eared Owl
The Short-eared Owl is a species of typical owl . In Scotland this species of owl is often referred to as a cataface, grass owl or short-horned hootlet. Owls belonging to genus Asio are known as the eared owls, as they have tufts of feathers resembling mammalian ears. These "ear" tufts may or may...

, Northern Harrier, Red-tailed and Swainson's Hawk
Swainson's Hawk
The Swainson's Hawk , is a large buteo hawk of the Falconiformes, sometimes separated in the Accipitriformes like its relatives. This species was named after William Swainson, a British naturalist...

s, Golden Eagle
Golden Eagle
The Golden Eagle is one of the best known birds of prey in the Northern Hemisphere. Like all eagles, it belongs to the family Accipitridae. Once widespread across the Holarctic, it has disappeared from many of the more heavily populated areas...

, accipiter
Accipiter
The genus Accipiter is a group of birds of prey in the family Accipitridae, many of which are named as goshawks and sparrowhawks. They can be anatomically distinguished from their relatives by the lack of a procoracoid foramen. Two small and aberrant species usually placed here do possess a large...

s, raven
Raven
Raven is the common name given to several larger-bodied members of the genus Corvus—but in Europe and North America the Common Raven is normally implied...

s, and magpies. It seems to be quite tolerant of conspecifics from adjacent territories.

Hunting and feeding

The Ferruginous Hawk primarily hunts small to medium-sized mammals but will also take birds, reptile
Reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

s, and some insects. Mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

s generally comprise 80 to 90 percent of the prey items or biomass in the diet with birds being the next most common mass component. The diet varies somewhat geographically, depending upon the distribution of prey species, but where the range of the Ferruginous Hawk overlaps, the black-tailed jackrabbit
Black-tailed Jackrabbit
The black-tailed jackrabbit , also known as the american desert hare, is a common hare of the western United States and Mexico, where it is found at elevations from sea level to up to...

 is a major food species along with ground squirrel
Ground squirrel
The ground squirrels are members of the squirrel family of rodents which generally live on or in the ground, rather than trees. The term is most often used for the medium-sized ground squirrels, as the larger ones are more commonly known as marmots or prairie dogs, while the smaller and less...

s and pocket gopher
Pocket gopher
The pocket gophers are burrowing rodents of the family Geomyidae. These are the "true" gophers, though several ground squirrels of the family Sciuridae are often called gophers as well...

s. Depending upon the relative abundance of jackrabbits and ground squirrels, the latter could become the major food source. The white-tailed jackrabbit
White-tailed Jackrabbit
The White-tailed Jackrabbit , also known as the Prairie Hare and the White Jack, is a hare found in western North America. Briefly reputed to have been extirpated , it is now clear from observations, roadkilled specimens and historical records that white-tailed jackrabbits are still extant in...

 are occasionally prey and weigh about twice as much as a Ferruginous Hawk. Common prey items are:
  • Rodents:
    • Richardson's ground squirrel
      Richardson's Ground Squirrel
      Richardson's ground squirrel , or the flickertail, is a North American ground squirrel in the genus Urocitellus...

    • thirteen-lined ground squirrel
      Thirteen-lined ground squirrel
      The thirteen-lined ground squirrel , also known as the striped gopher, leopard ground squirrel, squinney, and as the leopard-spermophile in Audubon’s day, is a ground squirrel....

    • antelope ground squirrel
      Antelope squirrel
      The antelope squirrels or antelope ground squirrels are the genus Ammospermophilus of sciurids found in the southwestern United States and northern Mexico....

    • prairie dog
      Prairie dog
      Prairie dogs are burrowing rodents native to the grasslands of North America. There are five different species of prairie dogs: black-tailed, white-tailed, Gunnison's, Utah and Mexican prairie dogs. They are a type of ground squirrel, found in the United States, Canada and Mexico...

    • kangaroo rat
      Kangaroo rat
      Kangaroo rats, genus Dipodomys, are small rodents native to North America. The common name derives from their bipedal form: as they hop in a manner similar to the much larger kangaroo, although they are not related...

       (Ord's)
    • northern pocket gopher
      Pocket gopher
      The pocket gophers are burrowing rodents of the family Geomyidae. These are the "true" gophers, though several ground squirrels of the family Sciuridae are often called gophers as well...

    • vole
      Vole
      A vole is a small rodent resembling a mouse but with a stouter body, a shorter hairy tail, a slightly rounder head, smaller ears and eyes, and differently formed molars . There are approximately 155 species of voles. They are sometimes known as meadow mice or field mice in North America...

      s (various species)
    • mice
      Mouse
      A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...

       (white-footed and others)
    • muskrat
      Muskrat
      The muskrat , the only species in genus Ondatra, is a medium-sized semi-aquatic rodent native to North America, and introduced in parts of Europe, Asia, and South America. The muskrat is found in wetlands and is a very successful animal over a wide range of climates and habitats...

    • pocket mouse
      Pocket mouse
      Pocket mouse may refer to:* Perognathus sp.* Chaetodipus sp....

  • Other mammals:
    • long-tailed weasel
      Weasel
      Weasels are mammals forming the genus Mustela of the Mustelidae family. They are small, active predators, long and slender with short legs....

    • snowshoe hare
      Snowshoe Hare
      The Snowshoe Hare , also called the Varying Hare, or Snowshoe Rabbit, is a species of hare found in North America. It has the name "snowshoe" because of the large size of its hind feet and the marks its tail leaves. The animal's feet prevent it from sinking into the snow when it hops and walks...

  • Birds:
    • Horned Lark
      Shore Lark
      The Shore Lark , called the Horned Lark in North America, is a species of bird in the genus Eremophila.- Description :...

    • Western Meadowlark
      Western Meadowlark
      Not to be confused with Eastern MeadowlarkThe Western Meadowlark is a medium-sized icterid bird, about 8.5 in long. It nests on the ground in open country in western and central North America. It feeds mostly on insects, but also seeds and berries...

    • Sharp-tailed Grouse
      Sharp-tailed Grouse
      The Sharp-tailed Grouse, Tympanuchus phasianellus , is a medium-sized prairie grouse. It is also known as the sharptail, and is known as "fire grouse" or "fire bird" by Native American Indians due to their reliance on brush fires to keep their habitat open.-Taxonomy:The Greater Prairie-chicken,...

    • Ring-necked Pheasant
      Common Pheasant
      The Common Pheasant , is a bird in the pheasant family . It is native to Georgia and has been widely introduced elsewhere as a game bird. In parts of its range, namely in places where none of its relatives occur such as in Europe , it is simply known as the "pheasant"...

    • Gray Partridge
      Grey Partridge
      The Grey Partridge, Perdix perdix, also known as the English Partridge, Hungarian Partridge, or Hun, is a gamebird in the pheasant family Phasianidae of the order Galliformes, gallinaceous birds...

    • Chukar
      Chukar
      The Chukar Partridge or Chukar is a Eurasian upland gamebird in the pheasant family Phasianidae. It has been considered to form a superspecies complex along with the Rock Partridge, Philby's Partridge and Przevalski's Partridge and treated in the past as conspecific particularly with the first...

    • duck
      Duck
      Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...

      s
    • Northern Harrier
    • Short-eared Owl
      Short-eared Owl
      The Short-eared Owl is a species of typical owl . In Scotland this species of owl is often referred to as a cataface, grass owl or short-horned hootlet. Owls belonging to genus Asio are known as the eared owls, as they have tufts of feathers resembling mammalian ears. These "ear" tufts may or may...

    • Burrowing Owl
      Burrowing Owl
      The Burrowing Owl is a tiny but long-legged owl found throughout open landscapes of North and South America. Burrowing Owls can be found in grasslands, rangelands, agricultural areas, deserts, or any other open dry area with low vegetation. They nest and roost in burrows, such as those excavated...

    • Long-billed Curlew
      Long-billed Curlew
      The Long-billed Curlew, Numenius americanus, is a large North American shorebird of the family Scolopacidae. This species was also called "sicklebird" and the "candlestick bird". The species is native to central and western North America...

    • Black-billed Magpie
      Black-billed Magpie
      The Black-billed Magpie is a bird in the crow family that inhabits the western half of North America. It is notable for its domed nests, and for being one of only four North American songbirds whose tail makes up half or more of the total body length The Black-billed Magpie (Pica hudsonia) is a...

  • Reptiles:
    • bull snake
    • yellow-bellied racer
      Coluber constrictor
      Coluber constrictor is a species of nonvenomous, colubrid snakes commonly referred to as the eastern racers. They are primarily found throughout the United States, east of the Rocky Mountains, but they range north into Canada, and south into Mexico, Guatemala and Belize...

    • garter snake
      Garter snake
      The Garter snake is a Colubrid snake genus common across North America, ranging from Alaska and Canada to Central America. It is the single most widely distributed genus of reptile in North America. The garter snake is also the Massachusettsstate reptile.There is no real consensus on the...

  • Insects:
    • grasshopper
      Grasshopper
      The grasshopper is an insect of the suborder Caelifera in the order Orthoptera. To distinguish it from bush crickets or katydids, it is sometimes referred to as the short-horned grasshopper...

      s
    • cricket
      Cricket
      Cricket is a bat-and-ball game played between two teams of 11 players on an oval-shaped field, at the centre of which is a rectangular 22-yard long pitch. One team bats, trying to score as many runs as possible while the other team bowls and fields, trying to dismiss the batsmen and thus limit the...

      s
    • carabid beetles
    • a few other larger insects


  • These birds search for prey while flying over open country or from a perch. They may also wait in ambush outside the prey's burrow. Hunting may occur at any time of the day depending upon the activity patterns of the major prey species. A bimodal pattern of early morning and late afternoon hunting may be common. The hunting tactics can be grouped into seven basic strategies:
    • Perch and Wait – perching is on any elevated natural or man-made site
    • Ground Perching – the hawk will stand on the ground at a rodent burrow after initially locating it from the air. As the burrowing animal reaches the surface, the hawk rises into the air and pounces upon it even while it is still underneath the loose earth.
    • Low-level Flight – birds will course over the landscape within a few yards of the ground and pursue in direct, low level chases, or they will hunt from 40 to 60 ft (12.2 to 18.3 m) above the ground.
    • High-level Flight – birds will hunt while soaring, but the success rate is generally low.
    • Hovering – using quickened wing beats, often in times of increased wind
      Wind
      Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

      s, the birds will search the ground and drop on the prey.
    • Cooperative Hunting – mates have been known to assist each other.
    • Piracy – the Ferruginous Hawk has been observed gathering around a hunter shooting prairie dog
      Dog
      The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

      s, and to claim shot "dogs" by flying to them and mantling over them.


    In its "strike, kill, and consume" type of predation, the prey is seized with the feet and a series of blows may be meted out, including driving the rear talon into the body to puncture vital organs. Biting with the beak
    Beak
    The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...

     may also take place. Before bringing prey to the nest, the adults will often eat the head. At the nest, birds are plucked and mammal
    Mammal
    Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

    s torn into pieces before being fed to the young. Food caching has been noted, but not generally near the nest.

    Reproduction and life history

    Copulation occurs during and after nest building. The egg
    Egg (biology)
    An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...

    -laying period varies with latitude
    Latitude
    In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

    , weather
    Weather
    Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...

    , and possibly food
    Food
    Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...

     supply. In the Canadian parts of the range, laying occurs from the latter part of April through late June, whereas farther south laying occurs from about March 20 through mid May. The earliest recorded clutch was in January in Utah and laying could occur as late as July 3 in Canada. Egg-laying occurs at two-day intervals with incubation starting when the first egg is laid. Incubation
    Avian incubation
    Incubation refers to the process by which certain oviparous animals hatch their eggs, and to the development of the embryo within the egg. The most vital factor of incubation is the constant temperature required for its development over a specific period. Especially in domestic fowl, the act of...

     is shared by both sexes with each taking approximately the same number of shifts during the 32 day average incubation period. Replacement clutches following failure appears to be rare.

    Courtship flights seem to be limited in the accepted sense. Both sexes engage in high, circling flight but literature details are sketchy. Soaring activities may primarily be variations on territorial defense flights as opposed to courtship per se. The "flutter-glide" flight consists of a series of shallow, rapid wing beats interspersed with brief glides and may serve to advertise the territory. The "sky-dance" is stimulated by an intruder and consists of slow flight with deep, labored wing beats with irregular yawing and pitching that may terminate in steep dives. In the "follow-soar" maneuver, the male Ferruginous Hawk will fly below an intruder and escort it out of the territory.

    High perching occurs from prominent places around the nest, particularly early in the breeding cycle. Aggressive actions such as attacking, talon-grasping, and pursuit have been noted by some observers. Copulation begins before construction of the new nest, and increases in frequency until the start of egg laying. The passing of food may occur before the activity. The duration of copulation is from four to 18 seconds.

    The Ferruginous Hawk is one of the most adaptable nesters of the raptors, and will use tree
    Tree
    A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...

    s, ledges, rock
    Rock (geology)
    In geology, rock or stone is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic...

     or dirt outcrops, the ground
    Soil
    Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

    , hay
    Hay
    Hay is grass, legumes or other herbaceous plants that have been cut, dried, and stored for use as animal fodder, particularly for grazing livestock such as cattle, horses, goats, and sheep. Hay is also fed to pets such as rabbits and guinea pigs...

    stacks, nest platforms, power poles, and other man-made structures. Within some broad categories such as cliffs, the variety includes clay, dirt and rock substrates. Tree nests are typically in isolated trees or isolated clumps of trees in exposed locations. Authors differ as to whether ground nests are more successful than tree nests, but they are more susceptible to mammalian predation. Nest locations are reused frequently, but several nests may be built in an area. Typically, one or two alternate nests may exist but up to eight have been found on some territories.

    The nests are made of ground debris such as sticks, branches, and cattails. Old nests will be refurbished, or nests of other species may be taken over and refurbished with sticks being added on top of the old nests. Odd items such as paper, rubbish, barbed wire
    Barbed wire
    Barbed wire, also known as barb wire , is a type of fencing wire constructed with sharp edges or points arranged at intervals along the strand. It is used to construct inexpensive fences and is used atop walls surrounding secured property...

    , cornstalks, plastic
    Plastic
    A plastic material is any of a wide range of synthetic or semi-synthetic organic solids used in the manufacture of industrial products. Plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and/or reduce production costs...

     and steel
    Steel
    Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

     cable have been incorporated into nests. Bark from trees and shrubs will be used for lining along with grasses and cow dung. Bits and pieces of greenery are often added to the nest. Prior to the removal of the bison
    American Bison
    The American bison , also commonly known as the American buffalo, is a North American species of bison that once roamed the grasslands of North America in massive herds...

     from this bird's range, nesting material often included bison bones, fur and dung. Both sexes are involved with building the nests and bringing materials, but the male seems to be more involved in retrieving materials while the female arranges them in the structure.

    Clutch size varies from one to eight and is likely linked to food supply. The average clutch is three to four eggs, each 2.5 inches (6.4 cm) long and 2 inches (5.1 cm) wide. They are smooth, non-glossy and whitish in color, irregularly spotted or speckled and blotched with reddish-brown markings. There may be a concentration of darker pigments at the small end of the egg. Occasionally, the eggs are almost unmarked or have faint scribblings on them.

    The nestling period varies from 38 to 50 days with brooding primarily by the female. Males fledge at 38 to 40 days and the females as late as 50 days after hatching, or 10 days later than their male siblings as they take longer to develop. Nestlings lie or sit for the first two weeks, stand at about three weeks and walk soon after. By 16 or 18 days, they are able to feed on their own. Wing flapping starts about day 23 and by day 33 the young are capable of vigorous flapping and "flap jumps." The nestlings are sensitive to high temperature
    Temperature
    Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...

    s and seek shade however possible in the nest.

    Initial movement out of the nest is felt to be a response to heat stress as the young quickly move towards shade. The initial flight for the males is taken at 38 to 40 days while the slower-developing females fly about 10 days later. Post-fledging dependency upon the parents may last for several weeks. During the first four weeks after fledging, the young patrol increasingly large areas around the nest as they learn to hunt. Young hawks have killed prey as early as four days after fledging.

    The Ferruginous Hawk is single-brooded, and as in so many raptors, the number of young reared is tied closely to food supply. In areas where jackrabbit populations are the principal food source, the initial clutch sizes and the number of reared young vary closely with variations in the number of jackrabbits. Fifty percent loss of young has been reported in low jackrabbit years. Fledging rates of 2.7 to 3.6 young per nest have been reported during years of abundant food supply. The high potential clutch size allows for a quick response to increases in the prey base.

    Birds have been known to live for 20 years in the wild, but most birds probably die within the first five years. The oldest banded birds were recovered at age 20. First-year mortality has been estimated at 66 percent and the adult mortality at 25 percent. The reasons for mortality include illegal shooting, loss of a satisfactory food supply, harassment, predation, and starvation
    Starvation
    Starvation is a severe deficiency in caloric energy, nutrient and vitamin intake. It is the most extreme form of malnutrition. In humans, prolonged starvation can cause permanent organ damage and eventually, death...

     of nestlings during times of low food supply. Ground nests are susceptible to predation by coyotes, and nestlings may be preyed upon by Great Horned Owl
    Great Horned Owl
    The Great Horned Owl, , also known as the Tiger Owl, is a large owl native to the Americas. It is an adaptable bird with a vast range and is the most widely distributed true owl in the Americas.-Description:...

    s and Golden Eagle
    Golden Eagle
    The Golden Eagle is one of the best known birds of prey in the Northern Hemisphere. Like all eagles, it belongs to the family Accipitridae. Once widespread across the Holarctic, it has disappeared from many of the more heavily populated areas...

    s.

    Status and conservation

    At times the Ferruginous Hawk has been considered threatened, endangered, or of concern on various threatened species lists but recent population
    Population
    A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

     increases in local areas, coupled with conservation
    Conservation biology
    Conservation biology is the scientific study of the nature and status of Earth's biodiversity with the aim of protecting species, their habitats, and ecosystems from excessive rates of extinction...

     initiatives, have created some optimism about the bird's future. It was formerly classified as a Near Threatened
    Near Threatened
    Near Threatened is a conservation status assigned to species or lower taxa that may be considered threatened with extinction in the near future, although it does not currently qualify for the threatened status...

     species by the IUCN, but new research has confirmed that the Ferrugineous Hawk is common and widespread again. Consequently, it was downlisted to Least Concern
    Least Concern
    Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...

     status in 2008.

    Declines are mostly due to loss of quality habitat. Although flexible in choosing a nest site and exhibiting a high reproductive potential, this bird's restriction to natural grasslands on the breeding grounds and specialized predation on mammals persecuted on rangelands may make conservation a continuous concern. Historically, the birds entirely disappeared from areas where agriculture displaced the natural flora and fauna; for example it was noted in 1916 that the species was "practically extinct" in San Mateo County, California
    San Mateo County, California
    San Mateo County is a county located in the San Francisco Bay Area of the U.S. state of California. It covers most of the San Francisco Peninsula just south of San Francisco, and north of Santa Clara County. San Francisco International Airport is located at the northern end of the county, and...

    . Studies have found that prairie dog
    Prairie dog
    Prairie dogs are burrowing rodents native to the grasslands of North America. There are five different species of prairie dogs: black-tailed, white-tailed, Gunnison's, Utah and Mexican prairie dogs. They are a type of ground squirrel, found in the United States, Canada and Mexico...

    s can be a main prey item for Ferruginous Hawks, linking them to the populations of prairie dog towns in the mid-west and southwestern United States, which have been declining in recent years. This bird may also be sensitive to the use of pesticide
    Pesticide
    Pesticides are substances or mixture of substances intended for preventing, destroying, repelling or mitigating any pest.A pesticide may be a chemical unicycle, biological agent , antimicrobial, disinfectant or device used against any pest...

    s on farms; they are also frequently shot. Threats to the overall population include:
    • cultivation of native prairie grassland and subsequent habitat loss
    • tree invasion of northern grassland habitats
    • reductions in food supply due to agricultural pest management programs
    • shooting and human interference


    The Ferruginous Hawk was on the National Audubon Society
    National Audubon Society
    The National Audubon Society is an American non-profit environmental organization dedicated to conservation. Incorporated in 1905, Audubon is one of the oldest of such organizations in the world and uses science, education and grassroots advocacy to advance its conservation mission...

    's "Blue List" of species felt to be declining. From 1971 to 1981 it retained its "blue" status, and from 1982 to 1986 it was listed as a species of "Special Concern." The United States Fish and Wildlife Service placed it in a category of "undetermined" in 1973, and various states have placed it in categories of "Threatened" or "Endangered." In Canada
    Canada
    Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

    , the Committee on the Status of Endangered Wildlife in Canada considered this species "Threatened" in 1980.

    Across the Canadian prairies, the range was diminishing up until 1980, and at that time, birds were felt to be occupying 48 percent of its original range. Numbers were generally felt to be diminishing and a total Canadian population was estimated at 500 to 1000 pairs. By 1987, population increases were being noted, and the Alberta population alone was estimated at 1,800 pairs. The upswing was likely due to a greater availability of food on the wintering grounds, making the birds more likely to breed when they returned to Canada. In the United States, there has been a history of concern for this species in many states with declines noted, but in 1988, one study suggested that the population in California and locally elsewhere may have increased significantly. The wintering population north of Mexico was estimated at 5,500 birds in 1986. In 1984, the population estimate for North America was between 3,000 and 4,000 pairs, and in 1987, it was 14,000 individuals.

    Toxic chemicals have not been suggested as a significant threat to the Ferruginous Hawk. Management strategies must include the retention or reclamation of native grasslands for breeding as well as on the wintering grounds. Maintenance of high populations of prey species in wintering areas seems critical to the hawks' abilities to move onto the summer range in breeding condition. The integration of agricultural practices and policies into the management strategies is a crucial component of any overall scheme for conservation. The provision of nesting platforms has had positive effects and should be a part of local strategies. Public education and the elimination of persecution and human disturbance must be an important part of the overall conservation program.

    External links

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