San Francisco State University
Biogeography of Red-tailed hawk (Buteo jamaicensis)
by Jeff Garrigues, student in Geography 316, Fall 2000
photograph by Moose Peterson. Copyright protected.
Species: ( Buteo jamaicensis)
Description of Species:
In general Red-tailed hawks are characterized by their stout, robust bodies, a broad wingspan, and red tail feathers. The exact appearance of the Red-tailed hawk varies throughout different subspecies. The most common subspecies found in California is the Western Red-tailed hawk (Buteo calurus), which ranges from dark to lighter colored morphs. Both sexes are alike in plumage and overlap considerably in size (Clark, 1987). Adults have shorter tails and broader wingspans than juveniles. When perched an adult Red-tailed hawk's wing tips will reach the tip of it's tail. Most Red-tailed hawks have lighter undersides with a dark belly band that varies in size. Typically light morph birds have darker heads. When viewed head on while flying many Red-tailed hawks show light areas on the leading edge of their wings that resemble headlights (Clark, 1987).
length: 17-22 inches
wingspan: 43-56 inches
weight: 1.5-3.3 pounds
(Wheeler & Clark, 1995)
Throughout North America the Red-tailed hawk is common, and often abundant. The variety of habitat that Red-tails are known to occupy include desert, deciduous woodland, tropical rain forest, agricultural fields with some elevated perching sights, and urban parks to name a few. The only habitat that the Red-tailed hawk does not occupy are dense forest areas and regions north of the tree line (Clark,1987). Red-tails are so versatile that in the Southwest region of the United States they are known to nest on cacti (Heintzelman,1979). This highly adaptive species may be second only to the Peregrine falcon in tolerance of diverse habitats in North America (Johnsgard,1990). One possible limiting factor in regards to Red-tail habitat is the availability of perching sites to hunt from (Heintzelman,1979). Preston and Beane (1993) note that the range of the Red-tailed Hawk has increased over time because of forest clearing for agricultural use and urban growth.
In north and central America there are 14 recognized subspecies of buteo jamaicensis: Here is a list and general location. The ranges of subspecies are not exclusive of one another.
B.j. alascensis: Southeastern Alaska to Vancouver Island
B.j. harlani: Southwestern Yukon to Northern B.C., Western Alaska up to the tree line
B.j. calurus: Western United States
B.j. kriderii: Canada south to Wyoming and Nebraska. Winters south to the Gulf coast
B.j. borealis: Eastern North America except Florida
B.j. umbrinus: Florida
B.j. fuertesi: Texas
B.j. fumosus: Mexico
B.j. socorroensis:Socorro Island, Mexico
B.j. hadropus: Mexican Highlands
B.j. kemsiesi: Guatemala to Nicaragua
B.j. costaricensis:Nicaragua to Panama
B.j. jamaicencis: Northern West Indies, except Bahamas and Cuba
B.j. solitudinus: Bahamas and Cuba
The diversity of prey for the Red tail hawk is
due to the raptors ability to modify its diet in order to adjust to local food
sources. What is interesting about this is that 2 hawks in the same area may develop
different food preferences (Johnsgard,1990). In a summarization of 11 studies on the
food intake of the Red tail hawk the diet compositions were estimated to be: 68%
mammal, 17.5% other birds, 7% reptiles and amphibians (mostly snakes), and 3.2%
invertebrates. (Johnsgard, 1990)
Mating behavior includes aerial courtships, which involve diving, and barrel rolls for a brief time. By locking their talons together the pair will spiral downward, release their grip and head back to the nest for copulation, often with the male grasping the female from above.
Breeding Pairs usually remain together until the death of one of the partners. Nest are constructed as early as December in warmer areas, but usually in late February (Preston&Beane, 1993). Johnsgard (1990) notes that there is a certain degree of nest reuse: In a study conducted in Michigan in 1976 it was found that 41% of nests studied were reoccupied a second year. But on the 3rd year only 13% of the nest were reoccupied.
The duration of time between nest selection and egg laying will range between 3 to 5 weeks (Preston & Beane, 1993). The female will lay 1 to 4 eggs (Johnsgard,1990). The male will do most of the hunting during the brooding period. Prey is torn into small pieces for the nesltings during the first 4-5 weeks. After this period prey is left in the nest for the nestlings to tear and eat (Preston & Beane, 1993).
Red-tailed hawks are diurnal birds of prey that hunt from both
soaring and perched positions. Red-tails can spot a small rodent from 100 feet in
the air.(photograph by Greg Gothard/copyright
Like all birds of prey Red-tailed hawks are protected by state and federal laws. But despite this some are killed by unethical hunters, and farmers that feel they are protecting chicken livestock (Georgia Wildlife Federation, 1998).
Classification tree with suggested evolution. Johnsgard,1990
Heintzelman(1979) notes that the
earliest fossils record for any bird is over 130 million years old. This was during
the upper Jurassic period. Archaeologist named the bird Archaeopteryx
lithographica, which means ancient wing preserved in stone. The fossil had many
skeletal features that are common with reptiles but was covered with feathers, which by
definition makes Archaeopteryx a bird.
Fossil records tell us very little about the evolution of raptors because the hollow, fragile bones of birds are not condusive to fossilization. Fossil records do tell us that buteos make their first fossil appearance during the upper Oligocene and Miocene epochs (about 25 million years ago.) These fossil relics were larger in size than the living counterparts (Heintzelman,1979). A variety of fossils appear during the Miocene epoch, and by the time the Pleistocene epoch began accipitrine hawks had evolved (Heintzelman,1979).
In California we have 3 very important bird bearing fossil deposits. First and most famous is the Rancho La Brea deposits in Los Angeles. This deposited contains fossils of birds which lived in a woodland area. The Mckittrick deposits of southern San Joaquin Valley feature fossils of birds that lived in a small desert lake, or a marsh. The Carpenteria beds are located along the ocean shore north of Ventura. Fossils found there are of birds that lived in coastal forest.
The La Brae tar pits were most abundant in fossils because species would become trapped and perfectly preserved. As an animal would begin to get stuck in the tar its cries would then attract birds of prey who were looking for an easy kill. Fortunately for our fossil records the birds would get stuck as well.
The Red-Tailed Hawk enjoys one of the widest distributions of any North American raptor. Year round distribution ranges from panama to the Canadian border, and from California to the east coast. They also have a breeding range that reaches as far north as central Alaska (Preston & Bean,1993).
The continuous distribution of the Red-tailed hawk is due to an abundance of food sources and the ability to adapt to a variety of habitat.
In an era where new species are constantly being added to endangered or threatened list it is refreshing to witness a very eurytopic species such as the Red-tailed Hawk thrive.
Map of Distribution:
Red-tailed hawks and Great horned owls (Bubo virginianus) as diurnal/nocturnal counterparts.
Both the Red-tailed hawk and the Great horned owl are extremely
adaptive predators that thrive in a diverse range of habitat. The two raptors
often co-exist in the same habitat with hawks hunting during the day, and owls at night.
Each species has a very general diet, will nest just about anywhere, and they are also
very similar in mass (Red-tailed hawk mean mass=1126g, Great horned owl mean mass 1354;
Marti & Kochert, 1995). The niches of most co-existing species
differ in up to three ways: habitat used for foraging, types of food eaten, and time
cycles of activity. The only significant differences between the niches of
Red-tailed hawks and Great horned owls are their diurnal/nocturnal feeding habits (Marti
& Kochert, 1995).
Even though the diurnal/nocturnal cycles reduce competition between the two there is still a small amount of interaction. Johnsgard (1990) notes that Great horned owls nest earlier in the year than Red-tailed hawks, and at times will claim a Red-tails nest
Preston, C.R., Beane, R.D., 1993. The Birds of North America. American Ornithologist Union vol. 2 no. 52
Clark, William S. 1987. A Field Guide to Hawks of North America. Boston, Mass. Houghton Mifflin Company.
Heintzelman, Donald S. 1979. Hawks and Owls of North America. New York, NY. Universe Books.
Wheeler, B.K., Clark, W.S. 1995. A Photographic Guide to North American Raptors. San Diego, CA. Academic Press Inc.
Johnsgard, Paul A. 1990. Hawks Eagles &Falcons of North America. Washington D.C. Smithsonian Institute Press.
Newton, Ian. 1979. Population Ecology of Raptors
Marti, Carl D., Micheal N. Kochert. 1995. "Are Red-Tailed Hawks and Great Horned Owls Diurnal-Nocturnal Dietary Couterparts?" The Wilson Bulletin Vol.197 n4
Georgia Wildlife Federation:
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