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Buteo brachyurusshort-tailed hawk

By Matthew Hasenjager

Geographic Range

Short-tailed hawks occur in the Nearctic and Neotropical regions. In the United States, short-tailed hawks reside mainly in southern Florida. In recent years they have been expanding their range northward to southern Texas, Arizona, and New Mexico, although no breeding has yet been reported in these states. Their range extends from the northern areas of Mexico to as far south as northern Argentina. A related taxon, Buteo albigula, which occurs in the temperate zone of the Andes and parts of Chile, was formerly considered a subspecies of short-tailed hawks but it is now generally given full species status.

Many populations appear to be migratory. Populations in Mexico may migrate as far south as Costa Rica. The population in Florida is disjunct by about 800 km from other populations and is partially migratory. In that population, individuals breed throughout most of the peninsula north to north-central Florida, but migrate during the winter to the southern tip of the peninsula and some of the Florida Keys. Populations from Panama and throughout South America are not known to migrate.

Habitat

Short-tailed hawks breed mainly in tall, dense, wet forest patches near water, such as mangrove and cypress swamps. When not breeding, individuals can be found near coastal areas, forests, forested edges, pine savannas, pastures, suburban areas, and open country. They are not usually found in dense, closed forest. While they often roost and nest in larger trees, they hunt primarily in open country and on forest edges, where wind conditions are best for their unique style of hunting. Buteo brachyurus occurs primarily in lowland and foothill habitats, typically up to 2000 m elevation and occasionally to 3000 m. Robinson et al. (1994) reports short-tailed hawks inhabiting a wide range of habitats in Amazonian Peru, including lake, rivers, pantanal (seasonally flooded wetlands mainly in southern Brazil), transitional forests, and upland forests, though they were considered rare in all of these except pantanal, where they were considered uncommon.

  • Range elevation
    3000 (high) m
    9842.52 (high) ft

Physical Description

Short-tailed hawks, one of the smaller species of Buteo, are crow-sized birds. They are 39 to 44 cm in length with a wingspan of 83 to 103 cm. The tail grows to 132 to 340 mm. Average mass is 441 grams. Females are larger than males, weighing on average 515 grams, while males weigh 392 grams on average. Though females are larger than males, the sexes are similar in the field. They have relatively long wings for their size; when perched, the wings reach the tail tip, giving these hawks their name due to the appearance of having an unusually short tail. In reality tail length is typical of the genus. The bill is black with a bluish-black base and a cere that varies from yellow to greenish-yellow. The legs and feet are light yellow to lemon yellow while the talons are black. The iris of Florida birds are dark brown in adults and lighter brown in juveniles. Museum specimens from tropical areas have irises ranging from yellow to yellowish-brown to brownish-yellow.

Short-tailed hawks occur in distinct light and dark color morphs with no intermediates. The light morph has white, unmarked underparts and underwing coverts while the head is a very dark blackish brown except for the anterior portions of the malar region, lores, chin, and throat, creating the effect of a dark hood. The upper parts and upper wing coverts are a uniform blackish brown with small patches of rufous brown on the sides of the upper breast, sides of the rump, and the scapulars. The tibial and crural feathers are pale buff. The under surface of the flight feathers is pale grayish with many narrow brownish bars and one wide dark terminal band along the trailing edge of the wing. The primaries are palest at the base of the outer first through fifth primaries, creating a diagnostic white oval. The rectrices appear grayish-brown above and grayish-white below with 4 to 5 narrow, incomplete brown bands and a dark terminal band. The tip of the tail feathers are pale gray. Sexes are alike.

The dark morph is almost entirely blackish brown. It lacks the rufous brown on the rump and scapulars and there is a small white patch where the lore and forehead meet. The underwing coverts are dark blackish brown except for the greater secondary and primary underwing coverts, which are mottled with white. The rest of the underwing appears the same as the light morph. Sexes are alike. In Florida, the dark morph is more numerous than the white. In other parts of the species’ range, the dark morph is uncommon or nonexistent.

Immature light morph short-tailed hawks have pale buff or orange-buff on the breast, belly, crural feathers, axillaries, and underwing coverts. The dark bands on the tail are heavier and more numerous than those on the adult, they are all roughly the same width. There are dark-brown streaks on the side of the breast and the edge of the feathers of the nape, scapulars, back, rump, and wing coverts have pale-brown or pale-buffy coloration. Instead of the hood of the adult, light-morph juveniles have ear coverts finely streaked with buff or pale ocher. Dark morph immature hawks have white spots and streaks on their chin, throat, belly, breast, axillaries, and under wing coverts.

There are two recognized subspecies of Buteo brachyurus: B. b. brachyurus and B. b. fuliginosus. Buteo brachyurus brachyurus is found in in South America. It can be distinguished from Buteo brachyurus fuliginosus by having less barring on the tail and no rufous on the side of the neck. Buteo brachyurus fuliginosus is found in Panama and the rest of the North American range. Though they are considered part of the same subspecies, the population of hawks in Florida appears to be larger-bodied than those living in Central and South America. They also have more rufous on their hind neck.

  • Sexual Dimorphism
  • sexes alike
  • female larger
  • Range mass
    392 to 515 g
    13.81 to 18.15 oz
  • Average mass
    441 g
    15.54 oz
  • Range length
    39 to 44 cm
    15.35 to 17.32 in
  • Range wingspan
    83 to 103 cm
    32.68 to 40.55 in

Reproduction

The breeding season of short-tailed hawks is from late January to July. These birds are presumed to be monogamous. Courtship consists of the male circling and undulating above the female who is perched at the nest site. The male then presents prey or nest material to the female. They have also been observed to grasp each others’ talons in the air and tumble earthward. Copulation begins with the male descending and landing near or on the female. He proceeds to give a two-note squeal before mounting for 5 to 7 seconds. Though one male was observed to have had 2 mates over three years, there is little information on the duration of pair bonds. There is no assortative mating between the two color morphs. During the breeding season short-tailed hawks becomes quite secretive and can then be difficult to locate.

Females create a platform nest made of sticks, lining the interior with finer twigs and soft material such as Spanish moss during incubation and hatching. Males gather nest materials. Nests are around 0.6 to 0.9 meters wide and 0.3 meters deep. Normally, they are located towards the top of taller trees, 9 to 29 meters up, in cypress swamps or mangroves. Less often, nest sites are found in the interior of both closed and open woods and the edges of hammocks. One to three preliminary nests may be constructed before a final nest is chosen. Nests may be reused year after year, and new nests are always located around the same area as previous ones. Only one brood is raised per season.

Buteo brachyurus normally lays two eggs, although clutch size varies from one to three eggs. Typically they are an unspotted bluish-white, although some have reddish brown speckling around the larger end. The eggs are short elliptical or nearly oval shape. The length of time between eggs in a clutch is unknown. Incubation lasts between 34 and 39 days. Females incubate eggs while males provisio females with food.

At hatching, young are covered in white natal down and weigh from 35 to 55 grams. About 2.5 to 3 weeks after hatching, a second layer of gray down is grown. Nestlings are brooded almost continuously as females are absent from the nest less than 10% of the time. Chicks are fed 2 to 3 times a day by both parents. Siblicide has not been well-documented in the species, although observations in captivity suggest that it is a possibility. Length of time to fledging is unknown. One specimen had a mass of 415 grams at fledging. In an estimated 45% of nests, at least one young is successfully raised. The age at sexual maturity is unknown; however first-year birds have not been observed breeding. The timing of molts in this species is also unknown.

  • Breeding interval
    Short-tailed hawks breed once every year.
  • Breeding season
    Short-tailed hawks breed from January to July.
  • Range eggs per season
    1 to 3
  • Range time to hatching
    34 to 39 days

Short-tailed hawk males and females both care for their young until they are fledged and independent.

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan/Longevity

There is no information on lifespan or survivorship in short-tailed hawks. Recorded causes of death include being shot, as well as being hit by cars. Habitat destruction, especially of winter breeding grounds in Florida, may also contribute to death in short-tailed hawks. Ironically, short-tailed hawks have increased in density in some areas due to logging that has opened up more of the forest edge habitats that it prefers (Thiollay 1999). (Thiollay, 1999)

Behavior

Short-tailed hawks are infrequently seen perching. They are usually spotted while soaring high in the air, scanning for prey below or while hovering at updrafts near forest edges. One diagnostic characteristic useful in identification is that the outer primaries are distinctly upturned in flight while the rest of the wing is flat. They use thermals to gain altitude, spiraling around inside the column of air. They are most active 2 to 3 hours after sunrise to 1 to 2 hours before sunset when thermals are available. Once the desired altitude is reached, short-tailed hawks use the wind to keep themselves aloft. When prey is spotted, these hawks dive, with occasional mid-flight holds to adjust direction.

They are solitary for much of the year except when breeding, though occasionally groups of 3 to 11 have been seen during migration.

They preen 1 to 2 hours after sunrise or late in the day. These hawks may bask for 45 to 60 seconds with wings widespread and backs facing the sun.

  • Range territory size
    1.2 to 1.6 m^2

Home Range

Adult short-tailed hawks have territory sizes of 1.2 to 1.6 miles in diameter. Their territories generally have a long stretch of forest edge where deflected air makes for easy soaring and stands of large trees for roosting. Their territories are larger than those of the sympatric and similarly-sized red-shouldered hawks (Buteo lineatus). This difference is thought to be because of differences in prey abundance and ease of capture. Short-tailed hawks often chase broad-winged hawks (Buteo platypterus) and red-shouldered hawks (Buteo lineatus) away from their territories.

Communication and Perception

The voice of Buteo brachyurus is described as a high-pitched, prolonged “keeeea” and it is often given when humans approach the nest. They also give a "keeee" call at the nest site, especially when males return to incubating females. A "squeee" call is also given before or after copulation and sometimes by a female when she is receiving food from a male. During the non-breeding period, these birds are usually silent. Newly hatched chicks give chip calls singly or in series of 2 to 4. After about four days they will call for food with soft squeals.

Food Habits

Short-tailed hawks feed mostly on smaller birds. In Florida, over half their bird diet is made up of eastern meadowlarks (Sturnella magna) and red-winged blackbirds (Agelaius phoeniceus), likely due to the conspicuousness of these species. They prey on adults of these species and have not been observed feeding on nestlings. When hunting, they hover or soar 50 to 300 meters high, with outstretched wings and head held down. From this position, they can dive on birds below. They also prey on lizards, snakes, rodents, and occasional insects (wasps and grasshoppers). They can catch prey on the wing, as well as when the prey is on a conspicuous perch. Ogden et al. (1974) report hunting success to be relatively low (~11%) with only 12 of 107 attempts being successful over the course of 30 hours of observation. Nestlings produce pellets of indigestible material about 30x12 mm in size.

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • reptiles
  • insects

Predation

There are no known predators of adult short-tailed hawks. Crows have been known to rob the nest of eggs.

Ecosystem Roles

Short-tailed hawks are important predators, especially of birds, in the ecosystems they inhabit.

Economic Importance for Humans: Positive

Short-tailed hawks may aid farmers by occasionally preying on rodents that feed on their crops.

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

There are no known negative effects of short-tailed hawks on humans.

Conservation Status

Buteo brachyurus is listed as Least Concern on the IUCN Red List. Short-tailed hawks are protected under the US Migratory Bird Act. They are not given any special status on the US Federal Endangered Species list nor are they listed under CITES Appendix II. Though uncommon to rare throughout most of their range, short-tailed hawks are not currently threatened. The Florida population, however, is at risk due to its small size (estimated at 500 individuals), geographic isolation, poor breeding success, and continuing loss of prairie, swamp forest, and mangroves.

Other Comments

Recent phylogenies of the buteos based on mitochondrial DNA sequences place Buteo brachyurus in a clade with Buteo swainsoni, Buteo galapagoensis, Buteo solitarius, and Buteo albigula. All of these species are primarily Neotropical species, with only short-tailed hawks and B. swainsoni having significant presences in North America. It is hypothesized that these hawks had a common ancestor similar to B. swainsoni that was a long-distance migrant capable of colonizing distant oceanic islands.

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Matthew Hasenjager (author), Michigan State University, James Harding (editor, instructor), Michigan State University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

References

2008. "The Hawk Conservancy Trust" (On-line). Accessed June 10, 2007 at http://www.hawk-conservancy.org/priors/shorttailedhawk.shtml.

Clark, W. 1987. A Field Guide to Hawks of North America. Boston: Houghton Mifflin Company.

Farrand Jr., J. 1988. Eastern Birds. New York: McGraw-Hill Book Company.

Miller, K., K. Meyer. 2002. Short-tailed Hawk (Buteo brachyurus). Pp. 674(1-16) in A Poole, P Stettenheim, F Gill, eds. The Birds of North America: Life Histories for the 21st Century, Vol. 17, 1 Edition. Philadelphia: The Birds of North America Inc..

Miller, K., K. Meyer. 2008. "Short-tailed Hawk(Buteo brachyurus)" (On-line). The Birds of North America Online. Accessed December 04, 2007 at http://bna.birds.cornell.edu/bna/species/674.

Ogden, J. 1974. Short-tailed-hawk in Florida. 1. Migration, Habitat, Hunting Techniques,. The Auk, 91/1: 95-110.

Riesing, M., G. Kruckenhauser, E. Haring. 2003. Molecular phylogeny of the genus Buteo(Aves: Accipitridae) based on mitochondrial marker sequences. Molecular Phylogenetics and Evolution, 27/2: 328-342.

Robbins, C., B. Bruun, H. Zim. 1983. A Guide to Field Identification: Birds of North America. Wisconsin: Western Publishing Company, Inc..

Robinson, S. 1994. Habitat Selection and Foraging Ecology of Raptors in Amazonian. Biotropica, 26/4: 443-458.

Sibley, D. 2003. The Sibley Field Guide to Birds of Eastern North America. New York: Alfred A. Knopf, Inc..

Thiollay, J. 1999. Responses of an avian community to rain forest degradation. Biodiversity and Conservation, 8: 513-534.

Williams III, S., J. Delong, W. Howe. 2007. Northward Range Expansion by the Short-tailed Hawk, with the First Records for New Mexico and Chihuahua. Western Birds, 38/1: 2-10.

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