Bird Guide

>Buteo brachyurus (Short-tailed Hawk)

2012-02-19T22:10:00.000-08:00

Short-tailed Hawk

Short-tailed Hawk

Dark morph ("little black hawk"), immature male
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Subclass:	Neornithes
Infraclass:	Neognathae
Superorder:	Neoaves
Order:	Falconiformes (or Accipitriformes, q.v.)
Family:	Accipitridae
Genus:	Buteo
Species:	B. brachyurus
Binomial name
*Buteo brachyurus* Vieillot, 1816
Synonyms
Buteo fuliginosus

The Short-tailed Hawk (Buteo brachyurus) is an American bird of prey in the family Accipitridae, which also includes the eagles and Old World vultures. As a member of the genusButeo, it is not a true hawk and thus also referred to as a "buteo" or (outside North America) "buzzard". The White-throated Hawk (B. albigula) is a close relative and was formerly included in the species B. brachyurus.

Description

The Short-tailed Hawk is a small buzzard, about 16 in (40 cm) long with a 35-inch (90 cm) wingspan. Males average about 14 oz (400 g) and females approach 20 oz (over 500 g), but the size difference is slighter than in most birds of prey and the sexes are indistinguishable in the field. It has broad rounded wings, the tips of which are curved upwards while soaring, and a broad tail that despite the bird's name is of average length for a buteo in proportion to the body. Its call is a high-pitched scream similar to other buzzards.

One of the most interesting things about this bird is the melanistic "black" phase – this species occurs in two colour morphs, with no intermediates. The dark form predominates in Florida, where it is known as "little black hawk". The light form is common elsewhere in the species' range. In most of the North American buteos – e.g. the Red-tailed Hawk (B. jamaicensis) andSwainson's Hawk (B. swainsoni) – melanistic individuals are known, although wholly black plumage is comparatively rare. Only in the North American population of Buteo brachyurus does it seem to be the prevalent form.

The adult light morph has dark brown upperparts. The underparts are white, except that the tail and flight feathers are grey barred with dark. The immature is similar to the adult but the face is streaked rather than white, and the tail bands are of equal width, whereas the adult has a broad bar near the tail tip.

The adult dark morph has black-brown upperparts and underparts, apart from the tail and flight feathers, which are grey barred with dark as in the light morph but possibly with darker grey. The young bird has the same tail pattern as the light-morph immature, and the underparts are spotted with white.

For a long time, it was thought that the dark phase of the present bird was a distinct speciesButeo fuliginosus. For example, when Robert Ridgway discussed the Short-tailed Hawk collected at Oyster Bay, Lee County, Florida by W. S. Crawford on January 28, 1881, the question whether or not the black birds were of the same species as the light ones was not yet settled.

Range and ecology

Short-tailed hawks breed in the tropical and subtropical Americas from southeastern Brazil and northern Argentina north through Central America to northern Mexico, as well as in southern Florida, USA. This species is generally found below 4,500 ft (c. 2,000 meters) ASL and most common below 2,500 ft (c.1,400 meters). It is replaced by the White-throated Hawk (B. albigula) in the Andes of southern Colombia and south to central Argentina and Chile; the Short-tailed Hawk is found in the Cordillera Central and Cordillera Occidental of Colombia, while B. albigula occurs south of these locales. As far as is known, B. brachyurus is a year-round resident except that most of the Florida populationmigrates in winter to the southern tip of the state, including the Keys.

Most of what is known about its natural history has been studied in the Floridan population, and might not apply to birds at the south of the species' range. In general, this species is associated with woodland, often near water.

It apparently eats mainly smaller birds. The Short-tailed Hawk hunts from soaring flight, often at the borders between wooded and open areas. A frequent maneuver is "kiting" – coming to a stop, the bird heads into the wind, with its wings held stationary. It typically attacks prey with a nearly vertical swoop, sometimes pausing and then continuing downward in a "stair-step" manner. Typical prey ranges from a New World warbler (Parulidae) to a bobwhite (Colinus) in size. In Florida, icterids – namely the Red-winged Blackbird (Agelaius phoeniceus) and the Eastern Meadowlark (Sturnella magna) – make up the bulk of the prey. It also eats some frogs, lizards, large insects, as well as the occasional smallish mammal, such as a rodent. Among the heaviest prey recorded are young Common Marmosets (Callithrix jacchus) and similar small monkeys; these do not seem to form an important prey item however, and are only snatched when the opportunity presents itself.

The large stick nest is built in a tree; in Florida the Bald Cypress (Taxodium distichum) is a popular nesting tree of the Short-tailed Hawk. Its 1–3 eggs prer clutch are white, usually with dark spots and blotches.

The Short-tailed Hawk is uncommon and local in most of its range. But due to its wide extent of occurrence, it is not considered threatened by the IUCN.

>Buteo leucorrhous (White-rumped Hawk)

2012-02-19T22:08:00.000-08:00

White-rumped Hawk

White-rumped Hawk

Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Falconiformes (or Accipitriformes, q.v.)
Family:	Accipitridae
Genus:	Buteo
Species:	B. leucorrhous
Binomial name
*Buteo leucorrhous* (Quoy & Gaimard, 1824)

The White-rumped Hawk (Buteo leucorrhous) is a species of bird of prey in the Accipitridaefamily. It is found in Argentina, Bolivia, Brazil, Colombia, Ecuador, Paraguay, Peru, and Venezuela. Its natural habitat is subtropical or tropical moist montane forests.

>Buteo ridgwayi (Ridgway's Hawk)

2012-02-19T22:07:00.001-08:00

Ridgway's Hawk

Ridgway's Hawk
Conservation status
Critically Endangered (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Falconiformes (or Accipitriformes, q.v.)
Family:	Accipitridae
Genus:	Buteo
Species:	B. ridgwayi
Binomial name
*Buteo ridgwayi* (Cory, 1883)

Ridgway's Hawk (Buteo ridgwayi) is a bird of prey in the family Accipitridae, which also includes the eagles, hawks and Old World vultures. Despite the name, this bird is a Buteo buzzard and not a true Accipiter hawk.

The Ridgway's Hawk's original breeding range included Haiti and the Dominican Republic (which make up the island of Hispaniola) and some of the adjacent isles and keys. As of 2006, its only known population resides within Los Haitises National Park in the northeastern Dominican Republic, which is mostly covered by wet limestone forest.

This is a medium-sized, compact hawk, 36–41 cm long. The adult has brown-grey upperparts, greyish barred underparts with a reddish-brown wash, rufous-tinged thighs and a black-and-white barred tail. The male is greyer than the female. The legs and base of bill are yellow.

This bird feeds on small mammals, birds, lizards and snakes. It nests in the crowns of tall trees, with nest-building in February and March and egg-laying in March and April.

This bird is critically endangered due to clearance of its forest habitat and persecution by local farmers, who erroneously believe the species preys on domestic fowl, even though reptiles comprise up to 90% of its diet. It has an estimated population of 80–120 pairs, making it, along with the Bay-breasted Cuckoo (Coccyzus rufigularis), the most threatened bird of Hispaniola.

This bird is named after the ornithologist Robert Ridgway.

>Buteo magnirostris (Roadside Hawk)

2012-02-19T22:07:00.000-08:00

Roadside Hawk

Roadside Hawk

In Goiás, Brazil
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Falconiformes (or Accipitriformes, q.v.)
Family:	Accipitridae
Genus:	Buteo Lacépède, 1799
Species:	B. magnirostris
Binomial name
*Buteo magnirostris* (Gmelin, 1788)
Synonyms
Rupornis magnirostris

The Roadside Hawk (Buteo magnirostris) is a relatively small bird of prey found in Latin America. This vocal species is often the most common raptor in its range. It has many subspecies and is sometimes placed in the monotypic genus Rupornis instead of Buteo.

Description

The Roadside Hawk is 31–41 centimetres (12–16 in) long and weighs 250–300 grams (8.8–11 oz). Males are about 20% smaller than females, but otherwise the sexes are similar. In most subspecies, the lower breast and underparts are barred brown and white, and the tail has four or five grey bars. Twelve subspecies are usually recognised and there is significant plumage variation between these. Depending on the subspecies involved, the Roadside Hawk is mainly brown or grey. It is fairly common to observe a touch of rufous (i.e., a light reddish-brownish coloration) on the bird's wings, specially when it is in flight. Its call is a very high-pitched piercing squeak. The eyes of adult Roadside Hawks are whitish or yellow. As suggested by its specific name (magni = large;rostri = beak), its beak is relatively large.

The Roadside Hawk may be marginally the smallest hawk in the widespread genus Buteo, althoughRidgway's Hawk and the White-rumped Hawk are scarcely larger.In flight, the relatively long tail and disproportionately short wings of the Roadside Hawk are distinctive. It frequently soars, but does not hover.

Subspecies

The subspecies and their distributions are:

B. m. griseocauda Ridgway, 1873 – Mexico (south from Colima, Nuevo León and Tamaulipas, except Yucatán and Tabasco) south to northwest Costa Rica and west Panama (Chiriquí).
B. m. conspectus (Peters, 1913) – southeast Mexico (Tabasco and Yucatán Peninsula) and northBelize.
B. m. gracilis (Ridgway, 1885) – Cozumel and Isla Holbox, near Yucatán (Mexico).
B. m. sinushonduri Bond, 1936 – Bonacca Island and Roatán, off Honduras.
B. m. petulans van Rossem, 1935 – southwest Costa Rica and Pacific slope of west Panama toTuira River, and adjacent islands.
B. m. alius (Peters & Griscom, 1929) – San José and San Miguel, in Pearl Islands (Gulf of Panama).
B. m. magnirostris (Gmelin, 1788) – Colombia south to west Ecuador, east to Venezuela and the Guianas, and south to Amazonian Brazil (Madeira River east to Atlantic coast).
B. m. occiduus (Bangs, 1911) – east Peru, west Brazil (south of Amazon, west of Madeira River) and north Bolivia.
B. m. saturatus (P. L. Sclater & Salvin, 1876) – Bolivia, through Paraguay and southwest Brazil (southwest Mato Grosso) to west Argentina(south to La Rioja).
B. m. nattereri (P. L. Sclater & Salvin, 1869) – northeast Brazil south to Bahia.
B. m. magniplumis (Bertoni, 1901) – south Brazil, north Argentina (Misiones) and adjacent Paraguay.
B. m. pucherani (J. & E. Verreaux, 1855) – Uruguay and northeast Argentina (south to Buenos Aires Province).

Range and habitat

	Roadside Hawk calls Recorded in Brazil
Problems listening to this file? See media help.

The Roadside Hawk is common throughout its range: from Mexico through Central America to most of South America east of the Andes cordillera. It is found from the northern Caribbean coast of South America south to the northeastern parts of Argentina. With the possible exception of dense rainforests, the Roadside Hawk is well adapted to most ecosystems in its range. It is also an urban bird, and is possibly the most common species of hawk seen in various cities throughout its range – or perhaps just the most conspicuous one, as it becomes aggressive when nesting and has been recorded attacking humans passing near the nest.

Food and feeding

The Roadside Hawk's diet consists mainly of insects, squamates, and small mammals, such as young Common Marmosets and similar smallmonkeys which are hunted quite often.^[7] It will also take small birds, but far less often than generalists such as the related but larger White-tailed Hawk, or bird specialists like the more distantly related Aplomado Falcon. Mixed-species feeding flocks it encounters when hunting in open cerrado habitat are not particularly wary of it: they watch it lest the hawk come too close, but consider them hardly more of a threat than the diminutive American Kestrel.

>Buteo swainsoni (Swainson's Hawk)

2012-02-19T22:05:00.000-08:00

Swainson's Hawk

Swainson's Hawk

Light-morph adult
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Falconiformes (but see text)
Family:	Accipitridae
Genus:	Buteo
Species:	B. swainsoni
Binomial name
*Buteo swainsoni* Bonaparte, 1838
Synonyms
Buteo swainsonii (lapsus)

The Swainson's Hawk (Buteo swainsoni), 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. It is colloquially known as Grasshopper Hawk or Locust Hawk, as it is very fond of Acrididae (locusts and grasshoppers) and will voraciously eat these insectswhenever they are available.

Their breeding habitat is prairie and dry grasslands in western North America. They build a stick nest in a tree or shrub or on a cliff edge. This species is a long-distance migrant, wintering inArgentina; there is a single record of a vagrant from Norway

This species or its immediate predecessor is the ancestor of the Galápagos Hawk, as demonstrated by recent research. The latter diverged from the mainland birds perhaps 300,000 years ago, a very short time in evolution.

Description

Rufous-morph bird in Hereford, Arizona, on its way to the pampas

The Swainson's Hawk is a raptor, slightly smaller than a Red-tailed Hawk (B. jamaicensis). However, the Swainson's Hawk has a slightly longer wingspan and slimmer wings than other soaring hawks. In flight, it holds its wings in a slight dihedral; it tips back and forth slightly while soaring.

There are two main color variations. Over 90 percent of individuals are light-morph; the dark morph is most common in the far west of the range:

Light-morph adults are white on the underparts with a dark, reddish "bib" on the chest and a noticeable white throat and face patch. The underwings, seen as the bird soars, have light linings (leading edge) and dark flight feathers (trailing edge), a pattern unique among North American raptors. The tail is gray-brown with about six narrow dark bands and one wider subterminal band. The upperparts are brown. Juveniles are similar but dark areas have pale mottling and light areas, especially the flanks, have dark mottling. The chest is pale with some darker marks. The subterminal band of the tail is less obvious. Birds in their first spring may have pale heads because of feather wear.
Dark-morph birds are dark brown except for a light patch under the tail. There is a rufous variant that is lighter on the underparts with reddish bars. The tails of both these forms resemble those of the light morph.

Range and migration

Swainson's Hawk inhabits North America mainly in the spring and summer and winters in South America. Breeding areas include south-centralAlberta, central Saskatchewan, southwestern Manitoba, and west and southern Minnesota. They will breed as far north as east-central Alaska, and southwestern Yukon. Breeding continues south through the eastern parts of Washington and Oregon, locally to the central valley of California, Arizona, New Mexico, and most of Texas. The eastern part of its range includes Minnesota, northwestern Iowa, most ofNebraska, Kansas, and Oklahoma, and all but eastern Texas. It periodically occurs in Iowa and rarely in northwestern Missouri, northernIllinois, and southwestern Wisconsin.

Swainson's hawk migration route.
30 birds were fitted with satellite tracking devices to produce this map

Small populations winter in southeastern Florida and along the Texas coast, probably having failed to find the way south around the Gulf of Mexico. Individuals reported north of these areas in winter (for example, on Christmas Bird Counts) are almost invariably misidentified buteos of other species. Immature Swainson's hawks winter on the pampas of South America in Argentina, Uruguay, and southern Brazil. It is not known with certainty where most of the adults spend the winter.

Swainson's Hawk is probably the longest migrant of any North American raptor. The flight from breeding ground to South American pampas in southern Brazil or Argentina can be as long as 14,000 miles (22,400 km). Each migration can last at least two months.

They leave the breeding grounds from August to October. Fall migration begins each clear day on which a wind blows in the general direction of travel. Birds gain altitude by soaring in circles on a rising thermal and then set their wings and close their tails as they glide, slowly losing altitude until they find another thermal and rise with it. Thus, waves and small groups are strung out across the sky.

The birds gradually head southwards toward Central America where virtually the entirepopulation funnels through the Isthmus of Panama. Concentrations over locations like Ancon Hill, Balboa, and Panama City are spectacular. In the Andes, it migrates along a narrow corridor and rarely strays off course; for example, it was only recorded in the Serranía de las Quinchas of Colombia – just 100 km or so off its usual migration route – in 2000/2001.

In Brazil, migrating birds pass through the western states of Acre and Mato Grosso, while wintering birds may stray to the southern states of Paraná, Rio Grande do Sul and São Paulo. But surprisingly, the occasional Swainson's Hawk – including birds one or two years of age – has also been recorded in the eastern states ofMaranhão, Pará, Pernambuco, Piauí and Tocantins, thousands of kilometers away from their usual migration route and wintering grounds and sometimes in mid-summer. This suggests that individuals occasionally become lost during migration, and/or that they may spend a whole year in the tropical regions and range about, rather than just overwintering at one site.

In Uruguay, the first dedicated studies show it to be not uncommon but patchily distributed across the country in winter. Notably, it had been underreported in Flores and Paysandú Departments, where it seems in fact to be a regular visitor. In recent years, the first birds were seen in early November, and some stayed til late February. Numbers increase throughout November and peak in December, when flocks of many dozen roam the open lands. But many stay only for a scant few weeks before leaving again.

Spring migration broadens once the birds have passed through Mexico as they disperse through the breeding range. Migrant groups are noted in the southern U.S. states in March. The earliest Swainson's Hawks arrive in southern Canada in late March, with migration peaking from mid April onwards.

Ecology

Soaring light-morph adult

The habitat of Swainson's Hawk consists of open and semi-open country – deserts, grasslands and prairies – in both its breeding and wintering ranges. It favors wild prairie, hayfields, and pastures over wheat fields and alfalfa fields, which may offer its prey too much cover. It requires elevated perches for hunting and a supply of small mammals such as young ground squirrels as prey for its nestlings. The breeding distribution of the Swainson's hawk is tied very closely to the distribution of various small mammals for this reason. In Saskatchewan, for example, the distribution of Richardson's ground squirrel and the Swainson's hawk are precisely the same.

The Swainson's Hawk will defend its breeding territory from other buteos. Breeding densities may vary from one area to the next but averages one pair per 2.5 square miles (6.5 km²). The average home range estimate for this hawk is 1 to 2 square miles (2.5 to 5 km²). It gathers in groups for feeding and migrating. However, in each case, such gathering is not social, but motivated by good feeding or migrating conditions.

Swainson's Hawk, Red-tailed Hawk (B. jamaicensis) and Ferruginous Hawk (B. regalis) compete for territory, and defend territories against each other. In many parts of the plains these three species nest in the same general area and exploit much the same prey base. Although diets overlap greatly, habitats may not overlap as much. In Oregon, the Swainson's Hawk selects nesting trees having a different configuration than those used by Red-tailed or Ferruginous Hawks. In southern Alberta, different nesting habitats help reduce food competition, with the Swainson's Hawk favoring areas with scattered trees or riparian borders, while Red-tailed Hawks nest in stands of tall trees, and Ferruginous Hawks nest on the open plains.

Reduced reproductive success may result from the Swainson's Hawk's nesting proximity to these two other buteos. The Swainson's Hawk is generally tolerant of people. The bird is attracted to haying, mowing, and plowing operations. House Sparrows, European Starlings, and other small birds may nest in or near a Swainson's Hawk's nest.

In winter quarters, they are far more tolerant, though many birds will still fend for themselves. In Uruguay, the species likes largely open but broken (with rocks or woods) plains or low hills, where it can be seen to gather in larger groups. Groups of a few dozen birds are not uncommon. Flocks of over one hundred birds have been recorded several times, e.g. one that roamed the Cuchilla Marincho region south ofAndresito (Flores Department) in mid-late December 2005.

Hunting and food

Swainson's Hawks soar over open ground with wings held in a dihedral. It occasionally courses low over the ground like a Northern Harrier(Circus cyaneus) or hovers like a Rough-legged Hawk (B. lagopus). It commonly perches on the ground both during migration and on the breeding grounds. During migration, it typically roosts for the night on bare ground with scattered trees, a habit that distinguishes it from fellow long-distance migrants such as the Broad-winged Hawk (B. platypterus), which roosts in closed-canopy woodlands.

These birds patrol open areas or scan for prey from a perch; they may also catch insects in flight. They take advantage of insects turned up by farm equipment or driven out by fire. A hunting Swainson's Hawk will use several strategies. It hunts insects such as dragonflies ordobsonflies while in flight, flapping little as it rides a wind current and stoops upon a fly, grabbing it with its foot and immediately transferring the prey to its bill. It uses a similar strategy to grab individual free-tailed bats from flying streams of bats. Also, when dragonfly hordes are grounded by weather, Swainson's Hawk will stand near groups sheltering from the wind and pluck at individual insects. Swainson's Hawk closely follows both tractors and wild fires for injured or fleeing food. It will also run down insect prey on the ground. Occasionally a hawk will stand still on a dirt bank or elevated mound waiting for prey to appear. It commonly hunts from elevated perches such as telephone poles, stooping on prey when it is sighted.

Common Grasshopper, a favorite foods of Swainson's Hawk

Swainson's Hawk may be largely insectivorous except when nesting. Insect prey commonly taken includes grasshoppers, crickets, and locusts. Pairs bring vertebrate prey to their nestlings, relying heavily upon small mammals such as young ground squirrels, young cottontails, pocket gophers, mice, young jackrabbits, and, at least locally, small birds and other vertebrates including reptilesand amphibians. Birds taken include large birds such as Mallards, and Sage Grouse which may have been injured initially.

Other unusual bird species taken include American Kestrel, and young Short-eared Owls. More typical in size are young Lark Buntings taken at their fledging time. Reptiles, which can comprise large parts of a diet, include snakes such as racers, gopher snakes and striped whipsnakes, and lizards. Amphibians may include tiger salamanders and toads. Swainson's Hawk is an opportunistic feeder which responds quickly to local concentrations of food.

In Argentina, flocks of immature Swainson's Hawks feed on flocks of the migratory darnerdragonfly Rhionaeschna bonariensis, following the hordes of insects and feeding mostly on the wing. Local outbreaks of locusts may also be exploited for food by one or more age-classes of birds. The immatures wintering in southern Florida apparently feed upon either insects, mice, or both, when turned up from field plowing. They move from one freshly ploughed field to the next.

There is also some evidence that road-killed birds and animals are also consumed both on the wintering grounds and on the breeding grounds. The species commonly follows tractors and other agricultural equipment during haying or ploughing, where rodents are exposed for the hawks to capture, or insects are uncovered after crop cutting. The Swainson's Hawks have been known to hunt the edges of prairie wildfires.

Reproduction and life span

A Swainson's Hawk chick

When Swainson's Hawks arrive at their nesting sites in March or April, they may return to their original nests as these hawks are noted to be monogamous. Research indicates that they have a high degree of mate and territorial fidelity. This is unusual in a long-distance migrant. Seven to 15 days after the birds arrive, the males begin constructing nests on the ground, ledges or in a trees. The nest consists of twigs and grasses and can take up to two weeks to complete. New nests may be constructed, old nests refurbished, or abandoned nests of other species – namely corvids – are refurbished.

The courtship displays of Swainson's Hawk are not well known. One activity involves circling and diving above a potential nest site. The underwings and rump are flashed and the birds call. The display may end with one bird diving to land on the edge of the nest. Copulation occurs mainly in the morning and evening on the dead limbs of trees. The female may assume the receptive position without a prior display. During treading one of the birds calls.

Swainson's Hawks typically nest in isolated trees or bushes, shelterbelts, riparian groves, or around abandoned homesteads. Occasionally, a pair will nest on the ground or on a bank or ledge. Nest trees and bushes include ponderosa pine, Douglas-fir, spruce, cottonwood, domesticpoplar, aspen, elm, mesquite, willow, saguaro cactus, and soaptree yuccas. Nests are located from nine to 15 feet above the ground, often in the shaded canopy but near the top of the tree. Nests are flimsy structures, usually smaller than the nests of the Red-tailed Hawk, and often blow down after nesting season.

Juvenile Swainson's Hawk

Clutch size ranges from one to four eggs, but averages two to three. Each egg is elliptical in shape, about 2.25 inches (57 mm) long and 1.8 inches (46 mm) wide. The egg is smooth with fine granulations and the ground color is white, often tinted bluish or greenish. During incubation the shell color quickly wears to dull white. Some eggs are plain; others are lightly marked with spots and blotches of light brown. The incubation period is 34 to 35 days, with the female incubating while the male brings food.

Young Swainson's Hawks are fed small, young mammals. Flight feathers begin to emerge on the young at nine to 11 days. High nestling mortality often occurs when the young are 15 to 30 days old and may be a result of fratricide. The young begin to leave the nest for surrounding branches at 33 to 37 days, fledging occurs at about 38 to 46 days. The fledglings are dependent upon their parents for four to 5 weeks. This species has one brood a year and apparently does not lay replacement clutches.

The oldest wild Swainson's Hawk on record is 24 years. Swainson's Hawks die because of collisions with traffic, illegal shooting, electrocution, and even during severe prairie weather such as hailstorms. Wind storms and hail caused 30 percent nest failure in one study. When sharing agrove with nesting Great Horned Owls, the hawks suffer much egg loss due to owl predation. The species also suffers from frequent, unexplained egg infertility.

Status and conservation

Injured light-morph Swainson's Hawk recuperating in Zoo Boise

Swainson's Hawk has suffered population declines since the first half of the century and was Blue-listed in the United States from 1972 to 1982. It has since been placed on the National Audubon's List of Special Concern in 1986. It is now listed by the United States Fish and Wildlife Service as a Category 3C candidate. It should be noted that the Swainson's Hawk was removed from the active Federal list because it was found to be more abundant than previously thought; it is not considered a threatened species by the IUCN due to its wide overall range. It remains listed as a threatened species by the California Department of Fish and Game as it has been since 1983.

A major cause of Swainson's Hawk population decline was pesticide use in its wintering grounds of Argentina. Farmers there were using pesticides (DDT and monocrotophos) to control grasshopperand locust infestations, and the Swainson's Hawks were ingesting these pesticides in several different ways, but mainly by gorging themselves on the insects as they lay dying. The U.S. has worked with Argentine farmers to resolve this problem.

Swainson's Hawk has adapted well to grazing and pastureland and seems to be holding its own over much of its breeding range, from northern Mexico to the southern parts of the prairie provinces. However, far western populations, like that of Oregon, and southern California, have drastically declined, often due to habitat loss or incompatible agricultural practices. A possible reason for declines in parts of its range may be agriculturally motivated reductions in populations of both ground squirrels and grasshoppers, major seasonal foods.

Although often nesting close to human activity, some Swainson's Hawks are very easily disturbed at the nest and often desert, especially early in the season. The bird is often quite tame and an easy target for shooters traveling isolated prairie roads. The species may also be affected in ways yet to be understood by some insecticides and herbicides, including those used on its wintering grounds.

Observing Swainson's Hawk

Snake River Birds of Prey National Conservation Area

One of the best places to view the hawk is in the Snake River Birds of Prey National Conservation Area (NCA) in Idaho. Birds in the NCA are most frequently sighted in mid March, May, and June, in the early morning and evening when they are actively hunting. In April, Swanson's Hawks engage in more sedentary breeding and egg-guarding, and are thus more difficult to spot. In July, rising canyon temperatures make prey scarce, so many birds of prey migrate away.

Another good site to see Swanson's is the American Prairie Reserve in North Eastern Mt.

>Buteo platypterus (Broad-winged Hawk)

2012-02-18T21:54:00.000-08:00

Broad-winged Hawk

Broad-winged Hawk

Conservation status
Least Concern (IUCN 3.1)^[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Falconiformes
Family:	Accipitridae
Genus:	Buteo
Species:	Buteo platypterus
Binomial name
*Buteo platypterus* (Vieillot, 1823)

The Broad-winged Hawk (Buteo platypterus) is a small hawk of the genus Buteo. During the summer some subspecies are distributed over eastern North America, as far west as British Columbia and Texas; they then migrate south to winter in the neotropics from Mexico down to southern Brazil.Other subspecies are all-year residents on Caribbean islands. As in most raptors, females are slightly larger than males. Broad-winged Hawks' wings are relatively short and broad with a tapered, somewhat pointed appearance. There are two types of colouration: a dark morph with fewer white areas and a light morph that is more pale overall. Although the Broad-winged Hawk's numbers are relatively stable, populations are declining in some parts of its breeding range because of forest fragmentation.

Description

A Broad-winged Hawk at Isle Royale National Park

The Broad-winged Hawk is a relatively small bird, with a body size from 34 to 44 centimetres (13 to 17 in) in length and weighing anywhere from 265 to 560 grams (9.3 to 20 oz).As in most raptors, females are slightly larger than males. Broad-winged Hawks have relatively short and broad wings, pointed at the end, which have a tapered appearance unique to the species. The Broad-winged Hawk can grow a wingspan of 81 to 100 centimetres (32 to 39 in).Adults' bodies are a dark brown with a white belly and chest containing horizontal barring. While their tail can be a dark grey-black with white lines along the middle, base and tip.The young hawks have a slightly different colouring with more white and longitudinal barring instead of horizontal barring. There are two types of colouration: a dark morph with fewer white areas and a light morph that is more pale overall.The light morph of this bird is most likely to be confused with the Red-shouldered Hawk, but they have a longer, more heavily barred tail and wings with a solid rufous color in the adult which are usually distinctive. Rare dark morphs are a darker brown on both upperparts and underparts. Dark-morph Short-tailed Hawks are similar but are whitish under the tail with a single subterminal band.

Taxonomy

This species, Buteo platypterus, is in the family Accipitridae, which is placed in the order Falconiformes (or Accipitriformes). Currently thespecies is split up into six subspecies; each is named for its distribution, as listed below:

Buteo platypterus platypterus – Northern Broad-winged Hawk that occurs throughout much of continental eastern North America.
Buteo platypterus brunnescens – Puerto Rican Broad-winged Hawk that occurs in Puerto Rico.
Buteo platypterus cubanensis – Cuban Broad-winged Hawk that occurs in Cuba.
Buteo platypterus insulicola – Antigua Broad-winged Hawk that occurs in Antigua.
Buteo platypterus rivierei – Dominican Broad-winged Hawk that occurs in Dominica, Martinique and St. Lucia.
Buteo platypterus antillarum – Antillean Broad-winged Hawk that occurs in the Lesser Antilles from Saint Vincent and Grenada to Tobago, excluding Antigua.

Habitat and distribution

Broad-winged Hawks have a wide range in North America and South America, from southern Canada to southern Brazil. Their breeding range is in the northern and eastern parts of North America and some, not all, migrate in the winter to Florida, southern Mexico and northern South America. There are five subspecies that are endemic to the Caribbean that do not migrate. Thus, Broad-winged Hawks are partial migrants. Those subspecies that do migrate will fly in flocks of more than forty up to hundreds of thousands at heights anywhere from 550 metres (1,800 ft) to approximately 1,300 metres (4,300 ft). They soar using thermals to carry them through their journey of 3,000–6,000 kilometres (1,900–3,700 mi). Fall migration lasts for 70 days as birds migrate about 100 kilometres (62 mi) per day from North America, through Central America to South America without crossing salt water. The enormous flocks of soaring Broad-winged Hawks are termed kettles and are characteristic of many hawk migration spectacles in North America, such as at Hawk Cliff in Ontario, Hawk Ridge in Minnesota, Hawk Mountain in Pennsylvania, and the River of Raptors in Veracruz.

Broad-winged Hawks stay in areas up to an elevation of about 2,000 metres (6,600 ft). They breed in deciduous forests good for nesting and forage primarily in wetlands and meadows. While some birds have acclimatized themselves to living near humans even those birds avoid human settlements and interactions. In the winter the migrating subspecies of the hawks seek out similar conditions to their overwinteringhome, so they settle in deciduous and mixed forests.

Although the Broad-winged Hawk's numbers are relatively stable, populations are declining in some parts of its breeding range because of forest fragmentation. Since there are no threats to its survival, it is assessed as Least Concern on the IUCN Red List.

Behaviour

Vocalization

These hawks use vocalizations for communication with their mates and offspring. Also in territorial displays towards intruders like the Red-tailed Hawks or other threatening animals. The call sounds like a very high pitched kee-ee, almost like a whistle. When confronted with a threat Broad-winged Hawks will emit an alarm call consisting of stuttered and squealing whistles.

Diet

Broad-winged Hawks are carnivores. The types of food they eat depends on the time of year. During the summer or nesting season the parents and ultimately their chicks will eat small mammals, such as chipmunks, shrews, and voles, frogs, lizards, and sometimes even other nesting birds. In the winter months Broad-winged Hawks have been observed feeding on insects, frogs, snakes, crabs, and some smallmammals. To catch their prey Broad-winged Hawks will watch from low branches hiding in the foliage until a target is spotted. From their roost they will do a short fast glide to capture the prey. They give special attention to preparing their food for consumption, skinning frogs and snakes and plucking prey birds' feathers. Most small mammals on the other hand will be eaten whole. They rarely drink water and are able to survive solely with the water present in their prey.

Reproduction

These birds will have only one mate during the breeding season, possibly because the male also helps a small amount with the upbringing of the chicks.They will breed anywhere between April and August starting when they are two years old; completely sexually developed.To attract and court females the males will do a flight display including cartwheels, birds meet in air hooking together by their talons and spiraling down together, dives, and other aerial acrobatics. They will also compete and fight with other males for the chance to mate with a female. If one of the males is successful the mating pair will have only one brood per season consisting of one to four eggs. Both the male and female will build the nest out of sticks and twigs in a deciduous tree before the eggs are to be laid. Once they are though the brown-spotted eggs are usually 49 by 39 millimetres (1.9 × 1.5 in) and weigh about 42 grams (1.5 oz). The female will then develop a brood patch and incubate the eggs for 28 days or longer before they hatch. The hatchlings will appear semi-altricial; incapable of any complex coordination but have open eyes and are covered in down feathers.Chicks will have rapid body growth until they are almost at adult body size at which time they are capable of walking, flying and eating without parental help. While in the nest the female gives most of theparental care, protecting and taking care of the chicks. It is not unusual to have the male provide some food for the female and offspring but his visits are short lived. Once a prey item is obtained for the nest the female will tear off pieces and will feed the chicks till they are able to rip meat off on their own. Often the chicks will fight for possession of the offered morsel, the younger ones usually losing and not getting enough. Broad-winged Hawks will protect their nests in a show of aggression (i.e. diving and chasing) towards any suspected threat but they generally will not make physical contact. Predators of eggs and nestlings includes raccoons, crows, porcupines and American Black Bears and adults have been know to fall to Great Horned Owls and Bald Eagles. It will take the hatchlings five to six weeks before they are able to leave the nest. Some young even after that time will remain in the area of the nest for several weeks more.

>Buteo lineatus (Red-shouldered Hawk)

2012-02-18T21:45:00.000-08:00

Red-shouldered Hawk

Red-shouldered Hawk

Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Falconiformes (or Accipitriformes, q.v.)
Family:	Accipitridae
Subfamily:	Accipitrinae
Genus:	Buteo
Species:	B. lineatus
Binomial name
*Buteo lineatus* (Gmelin, 1788)

The Red-shouldered Hawk (Buteo lineatus) is a medium-sized hawk. Its breeding range spans eastern North America and along the coast of California and northern to northeastern-centralMexico.

Description
Males are 43 to 58 centimetres (17 to 23 in) long, weigh about 550 g (19 oz) (1.2 lbs) and have a wingspan of 96 cm (38 in). Females are slightly larger at 48 to 61 cm (19 to 24 in) in length, a weight of about 700 g (25 oz), and a wingspan of about 105 cm (41 in). Adults have brownish heads, reddish chests, and pale bellies with reddish bars. Their tails, which are quite long by Buteo standards, are marked with narrow white bars. Red "shoulders" are visible when the birds are perched. These hawks' upper parts are dark with pale spots and they have long yellow legs. Western birds may appear more red, while Florida birds are generally paler. The wings of adults are more heavily barred on the upper side. Juvenile Red-shouldered Hawks are most likely to be confused with juvenile Broad-winged Hawks, but can be distinguished by their long tails, crescent-like wing markings, and a more flapping, Accipiter-like flight style. This bird is often confused with the Red-tailed Hawk.

Taxonomy

The Red-shouldered Hawk is a member of the genus Buteo, a group of medium-sized raptors with robust bodies and broad wings. Members of this genus are known as buzzards in Europe, but hawks in North America.

There are five recognized subspecies of Buteo lineatus, which vary in range and in coloration:

B. l. lineatus (Gmelin, 1788)
B. l. alleni
B. l. elegans
B. l. extimus
B. l. texanus

Behavior

Food and feeding

While in forested areas, these birds typically wait on a perch and swoop down on prey. When in clearings, they sometimes fly low to surprise prey. Small mammals are typically the most important prey, with voles, mice and chipmunks locally favored. Other prey can includeamphibians, reptiles (especially small snakes), small birds, and large insects. They will attack birds as large as pigeons and doves. During winters, they sometimes habituate to preying on birds commonly found at bird feeders. These birds are permanent residents throughout most of their range, though northern birds do migrate, mostly to central Mexico. The major modern threat to these birds is deforestation, which has eliminated these birds as breeders in some areas.

Breeding

The breeding habitats of the Red-shouldered Hawk are deciduous and mixed wooded areas, often near water. While establishing territories, the distinctive, screaming kee-aah call (usually repeated three to four times) of this bird is heard. The breeding pair builds a stick nest in a major fork of a large tree. The clutch size is typically three to four eggs. The blotchy-marked eggs are typically 54.5 × 43 mm (2.15 × 1.7 in). The incubation period can range from 28 to 33 days. The hatchlings, 35 g (1.2 oz) at first, are brooded for up to 40 days. The young leave the nest at about six weeks of age, but remain dependent on the parents until they are 17 to 19 weeks old. Predators of eggs and birds of all ages include Great Horned Owls, Red-tailed Hawks, Peregrine Falcons, raccoons, martens, and fishers (adults are vulnerable to the mammals only while nesting). Red-shouldered Hawks sometimes collaborate and peaceably coexist with American Crows (usually an enemy to all other birds because of their egg-hunting habits) to mob Great Horned Owls and Red-tailed Hawks. The clearing of forests over the last two centuries probably led to decreases in populations, while increasing habitat for the Red-tailed Hawk. Populations appear stable, but may be declining in some areas.

In art

John James Audubon illustrates the Red-shouldered Hawk in his book

	Red-shouldered Hawk Woodbridge, Connecticut, April 2002. By Tony Phillips.
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Gallery

Perched, taken in Northern Virginia
In Lighthouse Beach Park, Sanibel, Florida
In Carrboro, NC, 2007
With a kill
Red-shouldered Hawk taken in Dunwoody, GA, 2008
Cloisters City Park in Morro Bay, CA
Kanapaha Botanical Gardens, Gainesville, FL, 2008

>Buteo regalis (Ferruginous Hawk)

2012-02-18T21:42:00.000-08:00

Ferruginous Hawk

Ferruginous hawk

Light-morph immature in captivity
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Falconiformes (or Accipitriformes, q.v.)
Family:	Accipitridae
Genus:	Buteo
Species:	B. regalis
Binomial name
*Buteo regalis* (Gray, 1844)

The Ferruginous Hawk (ferruginous = from Latin ferrum - iron, ferrgin-, iron rust, iron-rust color - reddish-brown), Buteo regalis (Latin, royal hawk), is a large bird of prey and belongs to the broad-winged buteo hawks. An old colloquial name is "Ferrugineous Rough-leg", due to its similarity to the closely related Rough-legged Hawk (B. lagopus).

This species is a large, broad-winged hawk of the open, arid grasslands, prairie and shrub steppecountry; it is endemic to the interior parts of North America. It is used as a falconry bird in its native range.

Description

Dark-morph bird on nest

Light-morph in captivity

This is the largest of the Buteos and is often mistaken for an eagle 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 inches (51 to 69 cm) with an average of 23 inches (58 cm), wingspan from 48 to 60 inches (120 to 150 cm) with an average of 56 inches (140 cm), and weight from 2.1 to 5 pounds (950 to 2,300 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.

Voice

The voice is not well-described in literature. Alarm calls consist of kree - a or ke - ah and harsh kaah, kaah calls, the latter resembling some vocalizations of the herring gull. One description referred to the "wavering" alarm call and "breathy" notes, while other authors describe screams similar to those of the Red-tailed Hawk (B. jamaicensis).

Identification

In flight as seen from below

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 with dark legs. The back and wings are a brownish rust color. The head is white with a dark streak extending behind the eye. 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 wrists. 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 and semiarid grassland regions of North America. 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, and other arid shrub country. Nesting occurs in the open areas or in trees including cottonwoods, willows, and swamp oaks 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 mile (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 and Short-eared Owl, Northern Harrier, Red-tailed andSwainson's Hawks, Golden Eagle, accipiters, ravens, 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, reptiles, and some insects. Mammalsgenerally 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 is a major food species along with ground squirrels and pocket gophers. Depending upon the relative abundance of jackrabbits and ground squirrels, the latter could become the major food source. The white-tailed jackrabbit are occasionally prey and weigh about twice as much as a Ferruginous Hawk. Common prey items are:

Prairie dogs, one of the favorite foods of the Ferruginous hawk

Rodents:
- Richardson's ground squirrel
- thirteen-lined ground squirrel
- antelope ground squirrel
- prairie dog
- kangaroo rat (Ord's)
- northern pocket gopher
- voles (various species)
- mice (white-footed and others)
- muskrat
- pocket mouse
Other mammals:
- long-tailed weasel
- snowshoe hare

Birds:
Reptiles:
Insects:
- grasshoppers
- crickets
- 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 feet (12 to 18 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 winds, 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 dogs, and to claim shot "dogs" by flying to them and mantling over them.

A Ferruginous Hawk skull

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 may also take place. Before bringing prey to the nest, the adults will often eat the head. At the nest, birds are plucked and mammals 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-laying period varies with latitude,weather, and possibly food 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 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.

Ferruginous Hawk nesting platform

The Ferruginous Hawk is one of the most adaptable nesters of the raptors, and will use trees, ledges, rock or dirt outcrops, the ground, haystacks, 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, cornstalks, plastic andsteel 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 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.

Ferruginous Hawk chicks on nest

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 temperatures and seek shade however possible in the nest.

Juvenile Ferruginous Hawk

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 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 Owls and Golden Eagles.

Status and conservation

Banding Ferruginous Hawk chicks

At times the Ferruginous Hawk has been considered threatened, endangered, or of concern on various threatened species lists but recent population increases in local areas, coupled withconservation initiatives, have created some optimism about the bird's future. It was formerly classified as a Near Threatened species by the IUCN,^[7] but new research has confirmed that the Ferrugineous Hawk is common and widespread again. Consequently, it was downlisted to Least Concern 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. Studies have found that prairie dogs 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 pesticides 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'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, 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.