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Overview

Distribution

Range Description

This species has a large range from Mexico and Central America to Amazonia and south into Argentina.
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Geographic Range

Gray hawks (Asturina nitida) range from the Amazon Basin in South America into the southwestern United States. They are migratory in the northern part of their range, arriving in southern Arizona and extreme south Texas in the spring to breed, and occasionally entering New Mexico. These northern members of the species generally depart in mid-October to overwinter in Mexico, although they can be found in south Texas year-round, and rare records exist of winter residents in Arizona. Further south in their range, gray hawks are non-migratory (Glinski, 1998; Kaufman, 2000; Stiles and Skutch, 1989; Terres, 1980).

Biogeographic Regions: nearctic (Native ); neotropical (Native )

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Physical Description

Morphology

Physical Description

Gray hawks are medium-sized, woodland buteos, with shorter wings and longer tails than typical buteos. Adult birds have a slate-gray back, finely barred gray and white underparts, a black tail with two or three white bands, and a white rump. Juveniles have dark brown backs and buff-streaked underparts, brownish-gray tails with five to nine narrow black bars, and a dark brown eye stripe. Both adult and immature birds have dark gray or black beaks, brown irises, and yellow ceres and legs. Males are smaller than females. Gray hawks fly with accipiter-like movements, alternately flapping and gliding gracefully. Their flight pattern and gray color is similar to that of northern goshawks, which led to their other common name, “Mexican goshawks.” Northern goshawks, however, have a white eyebrow and lack the tail barring distinctive of gray hawks (Glinski, 1998; Kaufman, 2000; Stiles and Skutch, 1989; Terres, 1980; Wheeler and Clark, 1995).

Range mass: 378 to 660 g.

Average mass: 425 g.

Range length: 36 to 46 cm.

Range wingspan: 82 to 98 cm.

Average wingspan: 85 cm.

Other Physical Features: endothermic ; bilateral symmetry

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Ecology

Habitat

Habitat and Ecology

Systems
  • Terrestrial
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Throughout their range, gray hawks inhabit woodlands and arid deciduous forests. In the tropics they prefer dry second growth forest and thorn scrub. They tend to select patchy open forest, forest edges, and savanna trees. It is not uncommon to find them on agricultural fields. In denser woodland they tend to keep high in the forest canopy. Gray hawk northern breeding range is found in deciduous cottonwood-willow forests and mesquite bosques along riparian corridors or in evergreen oak woodlands (Glinski, 1998; Stiles and Skutch, 1989).

Range elevation: 0 to 1,800 m.

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: forest ; scrub forest

Other Habitat Features: agricultural ; riparian

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Trophic Strategy

Food Habits

Gray hawks are swift, agile fliers that can actively pursue prey by maneuvering through trees. They perch in the forest understory, locate prey in the trees or on the ground with their keen eyesight, and make short dashes to capture it whit their talons. They take reptiles, small mammals, birds, and some insects. In Arizona, Glinski (1988) studied food types delivered to nestlings and found that the diet was composed predominantly of terrestrial and arboreal lizards (74%), garter snakes (5%), nestling and adult birds (11%), and mammals (10%). Bibles’(1999) study of nest productivity in Arizona revealed similar findings, with reptiles comprising 68.6% of prey delivered to nestlings (all were lizards but for one snake), mammals 19.6% (rodents and one rabbit), birds 9.8%, and amphibians 2% (a toad).

Bibles (1999) also revealed that gray hawks prefer home ranges with taller trees and more open understory, probably because these enable them to observe their cryptic prey more easily. The increased flight space may also facilitate greater capture success. Mesquite bosques are the primary foraging areas of gray hawks breeding in Arizona because they have these characteristics. The amount of mesquite bosque seems to be the main factor that determines habitat quality in gray hawk nesting range in Arizona. (Amadon and Phillips, 1939; Bibles, 1999; Glinski, 1988; Glinski and Millsap, 1987; Gurrola-Hidalgo and Chavez, 1996; Stensrude, 1965).

Animal Foods: birds; mammals; amphibians; reptiles; insects

Primary Diet: carnivore (Eats terrestrial vertebrates)

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Associations

Ecosystem Roles

Gray hawks are important predators of smaller lizards and snakes throughout their range, though cryptic coloration, speed, and good hiding places can help some reptile prey evade capture. Gray hawks occasionally prey upon small birds. Smaller birds will often deter predation by mobbing birds of prey to drive them away. Olive-throated Parakeets have been seen mobbing a Gray Hawk to force it to leave the area (Eitniear et al., 1990).

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Predation

There are no documented cases of predation of gray hawks, but like other mid-sized hawks, they may be vulnerable to larger birds of prey. Raptor nestlings in the tropics may on rare occasions succumb to predation from arboreal hunters such as monkeys, coatis, snakes, and other birds, so it is possible that gray hawk nestlings may as well (Emmons and Feer, 1997).

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Known prey organisms

Asturina nitida preys on:
Insecta
Amphibia
Reptilia
Aves
Mammalia

This list may not be complete but is based on published studies.
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Life History and Behavior

Reproduction

Males court females with calls, undulating flight, and nest building.

Mating System: monogamous

Gray hawks from northern populations arrive in Arizona around mid-March to breed. Nest site fidelity is high, and gray hawk territories remain fairly constant from year to year. Pairs begin building the nest right after courtship, but they partition the work. The male builds the foundation, and the female shapes most of the bowl out of green, leafy twigs from the nest tree or neighboring trees. Northerly-breeding gray hawks primarily nest in cottonwood trees, but they will also nest in willow, ash, oak, hackberry, and mesquites. They choose nest sites in the upper third of the tree, usually in branches away from the trunk. Nests are crow-sized, about 60 cm across. The female usually lays two eggs in early May, although studies of nest productivity in Arizona have recorded nests with four or even eight eggs per clutch with a mean of 1.2 or 1.1 young per occupied breeding site. The eggs are white to pale blue and rarely marked. Only females incubate the eggs. Incubation lasts about 33 days, during which the male captures food for the female. After hatching, the young stay in the nest for about six weeks.

Arizona is the northernmost stronghold of breeding gray hawks, with nearly 80 known nest sites, most of which are protected in nature preserves or conservation easements. Six pairs also nest regularly along the Rio Grande River in south Texas. There is one reported incidence of nesting in New Mexico. Further south in their range, Gray Hawks are non-migratory and nest from December through May in tall, evergreen trees (Bibles, 1999; Brandt, 1951; Glinski, 1988; Glinski, 1998; Hubbard, 1974; Stiles and Skutch, 1989; Terres, 1980).

Breeding season: December through May

Average eggs per season: 1.2.

Range time to hatching: 32 to 34 days.

Average fledging age: 6 weeks.

Range age at sexual or reproductive maturity (female): 2 (low) years.

Range age at sexual or reproductive maturity (male): 2 (low) years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous

Females alone provide incubation, but the male feeds her. The male provides most of the food for the first two weeks post-hatching, after which the female begins to hunt as well. It is not known how quickly the young can hunt for themselves once they leave the nest.

Parental Investment: altricial ; male parental care ; female parental care

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Molecular Biology and Genetics

Molecular Biology

Barcode data: Buteo nitidus

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 3 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNAGTCGGCACCGCCCTCAGCCTACTTATCCGCGCAGAACTCGGCCAACCGGGCACACTCCTAGGTGATGACCAAATCTACAACGTAATCGTTACCGCACATGCCTTCGTAATAATTTTCTTCATAGTTATACCAATCATGATCGGAGGATTCGGAAACTGACTTGTCCCACTCATAATCGGCGCCCCCGACATAGCCTTCCCACGCATAAACAACATAAGCTTCTGACTACTTCCTCCATCCTTCCTCCTTCTCCTAGCCTCCTCAACAGTAGAAGCAGGGGCCGGCACCGGATGAACTGTCTATCCCCCACTAGCCGGCAACATAGCTCATGCTGGAGCTTCAGTAGACCTAGCCATCTTCTCCCTACACTTAGCCGGAGTTTCCTCCATTCTAGGGGCAATCAACTTTATCACAACCGCCATCAACATAAAACCCCCAGCTCTCTCCCAGTACCAAACACCCCTATTTGTATGATCTGTCCTCATTACCGCAGTCCTTCTACTACTCTCACTCCCAGTCCTAGCCGCCGGTATTACTATACTGCTTACAGACCGAAACTTAAACACAACATTCTTCGACCCCGCCGGCGGAGGTGNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
-- end --

Download FASTA File
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Statistics of barcoding coverage: Buteo nitidus

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 3
Specimens with Barcodes: 3
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2012

Assessor/s
BirdLife International

Reviewer/s
Butchart, S. & Symes, A.

Contributor/s

Justification
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
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Gray hawks have no special conservation status, although their limited numbers at the northern extreme of their range have led management agencies in Arizona to regard them as “sensitive species” and in Texas to consider them “threatened.” Arizona breeding populations seem to be holding steady, with reproduction balancing the losses from mortality. Fortunately, most of the 80 nest sites in Arizona today are located on protected lands. Concerned about how human demand for ground and surface water has seriously reduced desert riparian areas in the southwestern United States, private landowners and public and private conservation organizations have worked to set aside the remaining riparian corridors in southern Arizona. Further protection of the cottonwood-willow forests and mesquite bosques they support will demand protection of the waters that sustain them. If land managers succeed, this will be good news for gray hawks and the myriad other species that use these areas. Their only threat then would be recreational disturbance. Nesting gray hawks are sensitive to human activity near their nests, and many of the protected areas are frequented by recreational groups. Something as innocuous as a family picnic unknowingly staged near a nest tree can cause gray hawks to abandon their nest.

On their wintering range, other factors could lead to gray hawk decline. Glinski banded seven nestlings in Arizona that were recovered in northern Sinaloa state in Mexico, and six of these had been shot. The greatest threat on these wintering grounds, however, is habitat loss. There, the gray hawks’ thornscrub habitat is being widely cleared for agriculture. Gray hawks continue to persist along the living fence rows of trees that divide the agricultural fields, but it is unclear how many hawks this disrupted habitat can support, nor, ultimately, what effects this might have on Arizona’s breeding population. Little is known about demographics or conservation throughout the rest of the gray hawk's range (Glinski, 1988, 1998; Nabhan and Sheridan, 1977; Tellman et al., 1997; urls below).

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

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Population

Population
(Rich et al. 2004)

Population Trend
Unknown
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Positive

Since the range of gray hawks in the United States is so limited, many birdwatchers come to Arizona and Texas to see them. Bird watching has become increasingly important to the economy of southeastern Arizona. Just as the gray hawk's distribution barely extends into southern Arizona, so do the ranges of many other tropical and subtropical bird species. Several migratory species also use the area’s river corridors as they pass north from Mexico. Over 400 bird species draw birdwatchers from around the world. Their visitation has been an economic boon to the area. In 2001, visitors to two well-known birding spots in southeastern Arizona - Ramsey Canyon Preserve and the San Pedro Riparian National Conservation Area - spent an estimated $10.1 million to $16.9 million. About a third of the gray hawk nest sites in Arizona have been identified in the San Pedro NCR. While gray hawks are not the sole draw to the area, the numbers clearly illustrate the impact that conservation has on regional economies. Gray hawks, as well as people, stand to benefit from this perceived economic value. (Bibles, 1999; Relly, 2002; Viers, 2000).

Positive Impacts: ecotourism

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Wikipedia

Grey hawk

The Grey Hawk (Buteo plagiatus) is a smallish raptor found in open country and forest edges. It is sometimes placed in the genus Asturina as Asturina plagiata. The species has recently split by the AOU from the Grey-lined Hawk. The Grey Hawk is found from Costa Rica north into the southwestern United States.

The Grey Hawk is 46–61 cm (18–24 in) in length and weighs 475 g (16.8 oz) on average. The adult has a pale grey body, the tail is black with three white bands and the legs are orange. It is a solid, unpatterned gray on the upper parts.

Immature birds have dark brown upperparts, a pale-banded brown tail, brown-spotted white underparts and a brown streaked buff head and neck. This species is quite short-winged, and has a fast agile flight for a Buteo. The call is a shrill whistled kleee-ooo.

Grey Hawks feed mainly on lizards and snakes, but will also take small mammals, birds and frogs. It usually sits on an open high perch from which it swoops on its prey, but will also hunt from a low glide. The nest is of sticks and built high in a tree. The usual clutch is one to three, usually two white to pale blue eggs.[2] The young take about 6 weeks to fledging.

Taxonomy[edit]

The taxonomy of the Grey Hawk puts it within in the genus Buteo. This genus consists of hawks, which include the Red-shouldered Hawk, Swainson's Hawk, and others. The genus Buteo is in the sub-family Accipitrinae which is also known as the “true hawks,” and Accipitrinae is within the family of Accipitridae. Accipitridae consist of hawks, old world vultures, kites, harriers, and eagles. This family is within the order Falconiformes which are the diurnal, meaning during the day, birds of prey.[3]

The Grey Hawk was originally Asturina nitida but controversy existed between ornithologists on whether or not this species was closely enough related enough to put it in the Buteo, but chromosomal mapping in 2013 has proved that the Grey hawk is within the Buteoninae.[4] Researchers such as de Oliveira, Tagliarini, dos Santos, O'Brien, and Ferguson-Smith proposed in 2011 that the Gray Hawk should be two different species, because of a slight difference in plumage colour and a difference in alarm calls documented in the northern and southern distributional gap in Costa Rica. They suggest that the species is better split into the Grey-lined Hawk, Buteo nitidus and the Grey Hawk Buteo plagiatus),[5] but the American Ornithologist Union does not recognize the Grey Hawk as two different species. So far under the size range criteria this species' population is not vulnerable.

Description[edit]

The Grey Hawk averages 46–61 cm (18–24 in) inches in length and weighs 475 g (16.8 oz). This bird has a relatively short wing span, but long tail compared to the Red-tailed and Red-shouldered Hawks.[6] It has broad rounded wings, a hooked beak, and yellow legs.Thompson, L. (1995-2013).[7] It is very distinctive from its smooth pale grey plumage. The tail features are in a horizontal stripped pattern in a white gray white pattern with white at the tips of the tail feathers.[6] The tail feathers have two white bands with one being wider than the other.[7] The sexes are similar in coloration.[6] The adults, both male and female, have a darker grey top side with a lighter grey and white underside.[7] The juveniles have a dark brown topside and a streaked or spotted underside and the tail feathers have numerous dark bands.[7] The juveniles have very obvious bold facial strips and white upper tail coverts, which are the feathers at the base or start of the tail.[6] The juveniles also have a different plumage colour due to dominance and they use the dull colour for camouflage.

Distribution and habitat[edit]

A Grey Hawk’s range for the most part is in Central America and extends down into the Amazon and Northern Argentina in South America.[1] The range also can extend north into northern Mexico, southern New Mexico, southern Arizona, and southern Texas. Its habitat within this range consists of forest edges, river edges, clear cuts, savanna, and agricultural land (4). In their tropical range of the Amazon they tend to prefer a more dry second growth forest.

Behaviour[edit]

Diet[edit]

The grey hawk’s main diet is lizards and small birds, but it will also eat rodents and large insects. It hunts in brushy areas either from a perch or flight just above the canopy.

Migration[edit]

The migration of the gray hawks depend on the location in which a that animal’s home range is in. Birds that live in south-western United and Northern Mexico will migrate, but birds living further south are permanent residential of that area.[8] In a few occasions some birds in the northern range will not migrate and stay in the southern part of Texas year round, but this is rare. The birds that migrate north to the south-western United States will migrate in the spring in order to breed. After breeding season the birds will begin their journey back south in mid October to their wintering ranges.

Reproduction[edit]

The mating system of the Grey Hawk is monogamous. During December through May, the breeding season, these birds perform courtship displays (4). The males court the females by rising and falling flight, calls, and nest building. The male and female together will build their stick nest in tall trees, but the male only lays down the foundation while the female will shape the nest (9). The nest is about 60 centimeters across and the female will on average lay 2 to 3 pale-blue eggs per clutch. The female takes care of her eggs incubating them for 33 days; meanwhile the male will capture prey and bring it back to the female. A few breeding pairs nest along the Rio Grande in riparian woods (1). In research conducted from 1995-97 in south-west Arizona, it was found that gray hawks produced an average of 1.32 young per nest between all three years when the study was being conducted (8).[9] The chicks will begin fledging in 6 weeks and both males and females won’t hit sexual maturity until they are least 2 years of age.

Voice[edit]

The call of the Grey Hawk consists of long mournful whistles thoooooweeo, hoooooweeo .[6]

References[edit]

  1. ^ a b BirdLife International (2012). "Buteo nitidus". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ "Animal Diversity (Asturina nitida)". Retrieved 2008-06-26. 
  3. ^ The American Ornithologist Union. (2013). List of the 2,046 Bird Species (With Scientific and English Names) Known From the A.O.U. Check-List Area. The American Ornithologist Union. Retrieved November 10, 2013
  4. ^ de Oliveira E.H.C, Tagliarini M.M, dos Santos MS, O'Brien P.C.M., Ferguson-Smith M.A. (2013) Chromosome Painting in Three Species of orButeoninae: A Cytogenetic Signature Reinforces the Monophyly of South American Species. PLOS ONE.
  5. ^ Millsap, B.A, Seipke S.H., Clark W.S. (2011). The Gray Hawk (Buteo Nitidus) is Two Species. Condor. 113(2), pp. 326–339.
  6. ^ a b c d e Sibley, A. D., 2003. The Sibley Field Guide to Birds of Eastern North America. Andrew Stewart Publishing Inc. pp 101.
  7. ^ a b c d Buteo nitidus Gray Hawk Asturina nitida. Discover Life. Retrieved November 7, 2013
  8. ^ Rodríguez-Flores, C., Soberanes-González C., and Arizmendi M.C. (2010). Buteo nitidus. The Cornell Lab of Ornithology Neotropical Birds. Retrieved November 7, 2013
  9. ^ Bibles B.D., & Mannan R.A. (2004). Productivity and Nest-site Characteristics of Gray Hawks in Southern Arizona. Journal of Raptor Research. 38(3). pp. 238–242
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Grey Hawk

The Grey Hawk (Buteo plagiatus) is a smallish raptor found in open country and forest edges. It is sometimes placed in the genus Asturina as Asturina plagiata. The species has recently split by the AOU from the Grey-lined Hawk. The Grey Hawk is found from Costa Rica north into the southwestern United States.

The Grey Hawk is 46–61 cm (18–24 in) in length and weighs 475 g (16.8 oz) on average. The adult has a pale grey body, the tail is black with three white bands and the legs are orange. It is a solid, unpatterned gray on the upper parts.

Immature birds have dark brown upperparts, a pale-banded brown tail, brown-spotted white underparts and a brown streaked buff head and neck. This species is quite short-winged, and has a fast agile flight for a Buteo. The call is a shrill whistled kleee-ooo.

Grey Hawks feed mainly on lizards and snakes, but will also take small mammals, birds and frogs. It usually sits on an open high perch from which it swoops on its prey, but will also hunt from a low glide. The nest is of sticks and built high in a tree. The usual clutch is one to three, usually two white to pale blue eggs.[2] The young take about 6 weeks to fledging.

Taxonomy[edit]

The taxonomy of the Grey Hawk puts it within in the genus Buteo. This genus consists of hawks, which include the Red-shouldered Hawk, Swainson's Hawk, and others. The genus Buteo is in the sub-family Accipitrinae which is also known as the “true hawks,” and Accipitrinae is within the family of Accipitridae. Accipitridae consist of hawks, old world vultures, kites, harriers, and eagles. This family is within the order Falconiformes which are the diurnal, meaning during the day, birds of prey.[3]

The Grey Hawk was originally Asturina nitida but controversy existed between ornithologists on whether or not this species was closely enough related enough to put it in the Buteo, but chromosomal mapping in 2013 has proved that the Grey hawk is within the Buteoninae.[4] Researchers such as de Oliveira, Tagliarini, dos Santos, O'Brien, and Ferguson-Smith proposed in 2011 that the Gray Hawk should be two different species, because of a slight difference in plumage colour and a difference in alarm calls documented in the northern and southern distributional gap in Costa Rica. They suggest that the species is better split into the Grey-lined Hawk, Buteo nitidus and the Grey Hawk Buteo plagiatus),[5] but the American Ornithologist Union does not recognize the Grey Hawk as two different species. So far under the size range criteria this species' population is not vulnerable.

Description[edit]

The Grey Hawk averages 46–61 cm (18–24 in) inches in length and weighs 475 g (16.8 oz). This bird has a relatively short wing span, but long tail compared to the Red-tailed and Red-shouldered Hawks.[6] It has broad rounded wings, a hooked beak, and yellow legs.Thompson, L. (1995-2013).[7] It is very distinctive from its smooth pale grey plumage. The tail features are in a horizontal stripped pattern in a white gray white pattern with white at the tips of the tail feathers.[6] The tail feathers have two white bands with one being wider than the other.[7] The sexes are similar in coloration.[6] The adults, both male and female, have a darker grey top side with a lighter grey and white underside.[7] The juveniles have a dark brown topside and a streaked or spotted underside and the tail feathers have numerous dark bands.[7] The juveniles have very obvious bold facial strips and white upper tail coverts, which are the feathers at the base or start of the tail.[6] The juveniles also have a different plumage colour due to dominance and they use the dull colour for camouflage.

Distribution and habitat[edit]

A Grey Hawk’s range for the most part is in Central America and extends down into the Amazon and Northern Argentina in South America.[1] The range also can extend north into northern Mexico, southern New Mexico, southern Arizona, and southern Texas. Its habitat within this range consists of forest edges, river edges, clear cuts, savanna, and agricultural land (4). In their tropical range of the Amazon they tend to prefer a more dry second growth forest.

Behaviour[edit]

Diet[edit]

The grey hawk’s main diet is lizards and small birds, but it will also eat rodents and large insects. It hunts in brushy areas either from a perch or flight just above the canopy.

Migration[edit]

The migration of the gray hawks depend on the location in which a that animal’s home range is in. Birds that live in south-western United and Northern Mexico will migrate, but birds living further south are permanent residential of that area.[8] In a few occasions some birds in the northern range will not migrate and stay in the southern part of Texas year round, but this is rare. The birds that migrate north to the south-western United States will migrate in the spring in order to breed. After breeding season the birds will begin their journey back south in mid October to their wintering ranges.

Reproduction[edit]

The mating system of the Grey Hawk is monogamous. During December through May, the breeding season, these birds perform courtship displays (4). The males court the females by rising and falling flight, calls, and nest building. The male and female together will build their stick nest in tall trees, but the male only lays down the foundation while the female will shape the nest (9). The nest is about 60 centimeters across and the female will on average lay 2 to 3 pale-blue eggs per clutch. The female takes care of her eggs incubating them for 33 days; meanwhile the male will capture prey and bring it back to the female. A few breeding pairs nest along the Rio Grande in riparian woods (1). In research conducted from 1995-97 in south-west Arizona, it was found that gray hawks produced an average of 1.32 young per nest between all three years when the study was being conducted (8).[9] The chicks will begin fledging in 6 weeks and both males and females won’t hit sexual maturity until they are least 2 years of age.

Voice[edit]

The call of the Grey Hawk consists of long mournful whistles thoooooweeo, hoooooweeo .[6]

References[edit]

  1. ^ a b BirdLife International (2012). "Buteo nitidus". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ "Animal Diversity (Asturina nitida)". Retrieved 2008-06-26. 
  3. ^ The American Ornithologist Union. (2013). List of the 2,046 Bird Species (With Scientific and English Names) Known From the A.O.U. Check-List Area. The American Ornithologist Union. Retrieved November 10, 2013
  4. ^ de Oliveira E.H.C, Tagliarini M.M, dos Santos MS, O'Brien P.C.M., Ferguson-Smith M.A. (2013) Chromosome Painting in Three Species of orButeoninae: A Cytogenetic Signature Reinforces the Monophyly of South American Species. PLOS ONE.
  5. ^ Millsap, B.A, Seipke S.H., Clark W.S. (2011). The Gray Hawk (Buteo Nitidus) is Two Species. Condor. 113(2), pp. 326–339.
  6. ^ a b c d e Sibley, A. D., 2003. The Sibley Field Guide to Birds of Eastern North America. Andrew Stewart Publishing Inc. pp 101.
  7. ^ a b c d Buteo nitidus Gray Hawk Asturina nitida. Discover Life. Retrieved November 7, 2013
  8. ^ Rodríguez-Flores, C., Soberanes-González C., and Arizmendi M.C. (2010). Buteo nitidus. The Cornell Lab of Ornithology Neotropical Birds. Retrieved November 7, 2013
  9. ^ Bibles B.D., & Mannan R.A. (2004). Productivity and Nest-site Characteristics of Gray Hawks in Southern Arizona. Journal of Raptor Research. 38(3). pp. 238–242
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Grey-lined Hawk

The Grey-lined Hawk (Buteo nitidus) is a smallish raptor found in open country and forest edges. It is sometimes placed in the genus Asturina as Asturina nitida. The species has been split by the AOU from the Grey Hawk. The Grey-lined Hawk is found from southern Costa Rica to Argentina.

The Grey-lined Hawk is 46–61 cm (18–24 in) in length and weighs 475 g (16.8 oz) average. The adult has a pale grey body, the tail is black with three white bands and the legs are orange. It has fine white barring on the upper parts.

Immature birds have dark brown upperparts, a pale-banded brown tail, brown-spotted white underparts and a brown streaked buff head and neck. This species is quite short-winged, and has a fast agile flight for a Buteo.

It feeds mainly on lizards and snakes, but will also take small mammals, birds and frogs. It usually sits on an open high perch from which it swoops on its prey, but will also hunt from a low glide. The nest is of sticks and built high in a tree. The usual clutch is one to three, usually two white to pale blue eggs.[2] The young take about 6 weeks to fledging.

References[edit]

  1. ^ BirdLife International (2012). "Buteo nitidus". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013. 
  2. ^ "Animal Diversity (Asturina nitida)". Retrieved 2008-06-26. 
  • Baillie, J.E.M.; Hilton-Taylor, C. & Stuart, S.N. (eds.) (2004): 2004 IUCN Red List of Threatened Species. A Global Species Assessment. IUCN, Gland, Switzerland and Cambridge, UK. ISBN 2-8317-0826-5
  • ffrench, Richard; O'Neill, John Patton & Eckelberry, Don R. (1991): A guide to the birds of Trinidad and Tobago (2nd edition). Comstock Publishing, Ithaca, N.Y.. ISBN 0-8014-9792-2
  • Hilty, Steven L. (2003): Birds of Venezuela. Christopher Helm, London. ISBN 0-7136-6418-5
  • Stiles, F. Gary & Skutch, Alexander Frank (1989): A guide to the birds of Costa Rica. Comistock, Ithaca. ISBN 0-8014-9600-4
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