Buteo is a
genus of medium to fairly large, wide-ranging
raptors with a robust body and broad wings. In the Old World, members of this genus are called "
buzzards", but "
hawk" is used in the
New World (Etymology: Buteo is the
Latin name of the
common buzzard[1]). As both terms are ambiguous, buteo is sometimes used instead, for example, by the
Peregrine Fund.[2]
Characteristics
Buteos are fairly large birds. Total length can vary from 30 to 75 cm (12 to 30 in) and wingspan can range from 67 to 170 cm (26 to 67 in). The lightest known species is the
roadside hawk,[a] at an average of 269 g (9.5 oz) although the lesser known
white-rumped and
Ridgway's hawks are similarly small in average wingspan around 75 cm (30 in), and average length around 35 cm (14 in) in standard measurements. The largest species in length and wingspan is the
upland buzzard, which averages around 65 cm (26 in) in length and 152 cm (60 in) in wingspan. The upland is rivaled in weight and outsized in foot measurements and bill size by the
ferruginous hawk. In both of these largest buteos, adults typically weigh over 1,200 g (2.6 lb), and in mature females, can exceed a mass of 2,000 g (4.4 lb).[5][6][7][8] All buteos may be noted for their broad wings and sturdy builds. They frequently soar on thermals at midday over openings and are most frequently seen while doing this. The flight style varies based on the body type and wing shape and surface size. Some long-winged species, such as
rough-legged buzzards and
Swainson's hawks, have a floppy, buoyant flight style, while others, such as
red-tailed hawks and
rufous-tailed hawks, tend to be relatively shorter-winged, soaring more slowly and flying with more labored, deeper flaps.[5] Most small and some medium-sized species, from the
roadside hawk to the
red-shouldered hawk, often fly with an alternation of soaring and flapping, thus may be reminiscent of an Accipiter hawk in flight, but are still relatively larger-winged, shorter-tailed, and soar more extensively in open areas than Accipiter species do.[5][9] Buteos inhabit a wide range of habitats across the world, but tend to prefer some access to both clearings, which provide ideal hunting grounds, and trees, which can provide nesting locations and security.[6][7]
Diet
All Buteo species are to some extent opportunistic when it comes to hunting, and prey on almost any type of small animal as it becomes available to them. However, most have a strong preference for small
mammals, mostly
rodents. Rodents of almost every family in the world are somewhere preyed upon by Buteo species.[5][6][7] Since many rodents are primarily nocturnal, most buteos mainly hunt rodents that may be partially active during the day, which can include
squirrels and
chipmunks,
voles, and
gerbils. More nocturnal varieties are hunted opportunistically and may be caught in the first or last few hours of light.[5][7] Other smallish mammals, such as
shrews,
moles,
pikas,
bats, and
weasels, tend to be minor secondary prey, although can locally be significant for individual species.[5][7] Larger mammals, such as
rabbits,
hares, and
marmots, including even adult specimens weighing as much as 2 to 3 kg (4.4 to 6.6 lb), may be hunted by the heaviest and strongest species, such as
ferruginous,[7][10][11]red-tailed[12] and
white-tailed hawks.[13] Birds are taken occasionally, as well. Small to mid-sized birds, i.e.
passerines,
woodpeckers,
waterfowl,
pigeons, and
gamebirds, are most often taken. However, since the adults of most smaller birds can successfully outmaneuver and evade buteos in flight, much avian prey is taken in the nestling or fledgling stages or adult birds if they are previously injured.[5][7] An exception is the
short-tailed hawk, which is a relatively small and agile species and is locally a small bird-hunting specialist.[14] The
Hawaiian hawk, which evolved on an isolated group of islands with no terrestrial mammals, was also initially a bird specialist, although today it preys mainly on introduced rodents. Other prey may include
snakes,
lizards,
frogs,
salamanders,
fish, and even various
invertebrates, especially
beetles. In several Buteo species found in more tropical regions, such as the
roadside hawk or
grey-lined hawk, reptiles and amphibians may come to locally dominate the diet.[5]Swainson's hawk, despite its somewhat large size, is something of exceptional
insect-feeding specialist and may rely almost fully on
crickets and
dragonflies when wintering in southern
South America.[15][16]Carrion is eaten occasionally by most species, but is almost always secondary to live prey.[5] The importance of carrion in the Old World "buzzard" species is relatively higher since these often seem slower and less active predators than their equivalents in the
Americas.[17][18][19] Most Buteo species seem to prefer to ambush prey by pouncing down to the ground directly from a perch. In a secondary approach, many spot prey from a great distance while soaring and circle down to the ground to snatch it.[5]
Reproduction
Buteos are typical accipitrids in most of their breeding behaviors. They all build their own nests, which are often constructed out of sticks and other materials they can carry. Nests are generally located in trees, which are generally selected based on large sizes and inaccessibility to climbing predators rather than by species. Most Buteos breed in stable pairs, which may mate for life or at least for several years even in migratory species in which pairs part ways during winter. Generally from 2 to 4 eggs are laid by the female and are mostly incubated by her, while the male mate provides food. Once the eggs hatch, the survival of the young is dependent upon how abundant appropriate food is and the security of the nesting location from potential nest predators and other (often human-induced) disturbances. As in many raptors, the nestlings hatch at intervals of a day or two and the older, strong siblings tend to have the best chances of survival, with the younger siblings often starving or being handled aggressively (and even killed) by their older siblings. The male generally does most of the hunting and the female broods, but the male may also do some brooding while the female hunts as well. Once the fledgling stage is reached, the female takes over much of the hunting. After a stage averaging a couple of weeks, the fledglings take the adults increasing indifference to feeding them or occasional hostile behavior towards them as a cue to disperse on their own. Generally, young Buteos tend to disperse several miles away from their nesting grounds and wander for one to two years until they can court a mate and establish their own breeding range.[5][6][7]
Distribution
The Buteo hawks include many of the most widely distributed, most common, and best-known raptors in the world. Examples include the
red-tailed hawk of
North America and the
common buzzard of
Eurasia. Most
Northern Hemisphere species are at least partially migratory. In
North America, species such as
broad-winged hawks and
Swainson's hawks are known for their huge numbers (often called "kettles") while passing over major migratory flyways in the fall. Up to tens of thousands of these Buteos can be seen each day during the peak of their migration. Any of the prior mentioned common Buteo species may have total populations that exceed a million individuals.[5] On the other hand, the
Socotra buzzard and
Galapagos hawks are considered vulnerable to extinction per the
IUCN. The
Ridgway's hawk is even more direly threatened and is considered Critically Endangered. These insular forms are threatened primarily by
habitat destruction, prey reductions and poisoning.[5][6] The latter reason is considered the main cause of a noted decline in the population of the more abundant
Swainson's hawk, due to insecticides being used in southern
South America, which the hawks ingest through crickets and then die from poisoning.[20]
A number of
fossil species have been discovered, mainly in North America. Some are placed here primarily based on considerations of
biogeography, Buteo being somewhat hard to distinguish from Geranoaetus based on
osteology alone:[52]
†Buteo dondasi (Late Pliocene of Buenos Aires, Argentina)
†Buteo fluviaticus (Brule Middle? Oligocene of Wealt County, US) – possibly same as B. grangeri
†Buteo grangeri (Brule Middle? Oligocene of Washabaugh County, South Dakota, US)
^
abcdefghEagles, Hawks and Falcons of the World by Leslie Brown & Dean Amadon. The Wellfleet Press (1986),
ISBN978-1555214722.
^CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992),
ISBN978-0-8493-4258-5.
^Crossley, R., Liguori, J. & Sullivan, B. The Crossley ID Guide: Raptors. Princeton University Press (2013),
ISBN978-0691157405.
^Smith, D. G. and J. R. Murphy. 1978. Biology of the Ferruginous Hawk in central Utah. Sociobiology 3:79-98.
^Thurow, T. L., C. M. White, R. P. Howard, and J. F. Sullivan. 1980. Raptor ecology of Raft River valley, Idaho. EG&G Idaho, Inc. Idaho Falls.
^Smith, D. G. and J. R. Murphy. 1973. Breeding ecology of raptors in the East Great Basin Desert of Utah. Brigham Young Univ. Sci. Bull., Biol. Ser. Vol. 18:1-76.
^Kopeny, M. T. 1988a. White-tailed Hawk. Pages 97–104 in Southwest raptor management symposium and workshop. (Glinski, R. L. and et al., Eds.) Natl. Wildl. Fed. Washington, D.C.
^Ogden, J. C. 1974. The Short-tailed Hawk in Florida. I. Migration, habitat, hunting techniques, and food habits. Auk 91:95-110.
^Snyder, N. F. R. and J. W. Wiley. 1976. Sexual size dimorphism in hawks and owls of North America. Ornithol. Monogr. no. 20.
^Jaramillo, A. P. 1993. Wintering Swainson's Hawks in Argentina: food and age segregation. Condor 95:475-479.
^Tubbs, C.R. 1974. The buzzard. David & Charles, Newton Abbot.
^Wu, Y.-Q., M. Ma, F. Xu, D. Ragyov, J. Shergalin, N.F. Lie, and A. Dixon. 2008. Breeding biology and diet of the Long-legged Buzzard (Buteo rufius) in the eastern Junggar Basin of northwestern China. Journal of Raptor Research 42:273-280.
^Allan, D.G. 2005. Jackal Buzzard Buteo rufofuscus. P.A.R. Hockey, W.R.J. Dean, and P.G. Ryan (eds.). Pp. 526–527 in Roberts Birds of Southern Africa. VIIth ed. Trustees of the John Voelcker Bird Book Fund, Cape Town, South Africa.
^Weidensaul, S. Living on the Wind: Across the Hemisphere With Migratory Birds. North Point Press (2000),
ISBN978-0865475915.
^A complete left
ulna similar to Buteo but of distinctly small size: Cracraft (1969)
^Probably several species; similar to
Common Buzzard in appearance and size: Ballmann (1969), Mlíkovský (2002)
^Boev, Z., D. Kovachev. 1998. Buteo spassovi sp. n. - a Late Miocene Buzzard (Accipitridae, Aves) from SW Bulgaria. - Geologica Balcanica, 29 (1-2): 125–129.
"Raptors of the World" by Ferguson-Lees, Christie, Franklin, Mead & Burton. Houghton Mifflin (2001),
ISBN0-618-12762-3.
Alcover, Josep Antoni (1989): Les Aus fòssils de la Cova de Ca Na Reia. Endins14-15: 95-100. [In Catalan with English abstract]
Ballmann, Peter (1969): Les Oiseaux miocènes de la Grive-Saint-Alban (Isère) [The Miocene birds of Grive-Saint-Alban (Isère)]. Geobios2: 157–204. [French with English abstract]
doi:
10.1016/S0016-6995(69)80005-7 (HTML abstract)
Brodkorb, Pierce (1964): Catalogue of Fossil Birds: Part 2 (Anseriformes through Galliformes). Bulletin of the Florida State Museum8(3): 195–335.
PDF or JPEG fulltextArchived 2008-02-23 at the
Wayback Machine
Cracraft, Joel (1969): Notes on fossil hawks (Accipitridae). Auk86(2): 353–354.
PDF fulltext
Mlíkovský, Jirí (2002): Cenozoic Birds of the World, Part 1: Europe. Ninox Press, Prague.
ISBN80-901105-3-8PDF fulltext