Accipiter striatus
Sharp-shinned Hawk, a complex of 4 or more possible species (Howell and Webb 1995, Am. Ornithol. Union 1998, Bildstein and Meyer 2000). remains in need of further study, in spite of the extensive material cited by Bildstein and Meyer (2000). This is a difficult species to study. Its small size, sexual dimorphism, secretive nature and extensive range cause serious problems for researchers.
DISTRIBUTION. During the 1987-1992 field work seasons of the TBBA project, observers obtained a single confirmed breeding site in latilong 30096 and a probable site in 30097. A possible record was also found in 30096 and another in 30098 as well as another 8 sites northeast of these. To the south 6 more possible records were obtained, including 4 in 26098. In west Texas 6 possible records came from 31104 in the Guadalupe Mountains area. Breeding Bird Survey (BBS) observers found an average of <1 Sharp-shinned Hawk per route in this area. Only 10 BBS routes in Texas reported this hawk (Sauer et al. 2005). Lockwood and Freeman (2004) characterize this species as a very rare summer resident of Texas, primarily in the Pineywoods and higher elevations of the Trans-Pecos.
This species has a wide breeding range in the Western Hemisphere, extending from Alaska to Argentina, excluding grasslands, deserts and other non-forested areas. Sharp-shinned Hawks nesting in Alaska and Canada move south after breeding to winter throughout the United States, Mexico and Central America (Bildstein and Meyer 2000).
SEASONAL OCCURRENCE. Sharp- shinned Hawks wintering in or migrating through Texas are gone by early May. Year-round residents breed from April to August. Migrants and wintering birds begin arriving from the north in mid-September (Oberholser 1974, Lockwood and Freeman 2004).
BREEDING HABITAT. Sharp-shinned Hawks breed in Texas from about 40-2400 m (120-7900 ft) in open woodlands, patches of trees and thickets (Oberholser 1974). In Arizona and Colorado, this hawk is a montane breeder, using mostly coniferous forests (Levad 1998, Wise-Gervais 2005).
Sharp-shinned Hawk nests are most commonly found against the trunk of a conifer located in a thick stand of trees. The nest tree is usually mature and the nest is placed well below the canopy. The broad, flat structure is composed of sticks and twigs and is often unlined or topped with bark chips. The nest is similar in size to a Cooper’s Hawk (A. cooperii) nest with an outside diameter of about 61-66 cm (24-26 in), height 18 cm (7 in), inside diameter 15 cm (6 in) and cup depth 5-8 cm (2-3 in; Harrison 1979, Bildstein and Meyer 2000).
In this structure the female lays a clutch of 4-5 (range 3-8) smooth, off-white eggs, marked with brown, violet or hazel. The eggs are usually laid on alternate days. Incubation, mostly by the female, usually lasts 30-32 days and the young leave the nest about 21-27 days after hatching (Bildstein and Meyer 2000).
STATUS. This rare breeder in Texas becomes uncommon to common when migrants and winter residents are present (Lockwood and Freeman 2004). Although population trends for Texas are not available, data from 290 BBS routes in the United States and Canada produce a statistically significant annual population change of +3.7% for the period 1980-2005 (Sauer et al. 2005). The status of Sharp-shinned Hawk as a breeding bird in Texas is precarious. Although most breeding evidence obtained during the TBBA field work came from east Texas, nearby Oklahoma did not find breeding evidence in that state during their atlas period (Reinking 2004). In the western United States, breeding is generally restricted to higher elevations (Levad 1998, Bildstein and Meyer 2000, Wise-Gervais 2005), consistent with the TBBA possible reports from the Guadalupe Mountains and other reports (Lockwood and Freeman 2004). Even in these protected sites global climate changes may still threaten the habitat used by Sharp-shinned Hawks, making their long-term status as breeders in the Trans-Pecos problematic.
Text by Robert C. Tweit (2007)
Literature cited.
American Ornithologists’ Union. 1998. Checklist of North American birds, 7th ed. Am, Ornithol. Union, Washington, DC.
Bildstein, K. L. and K. Meyer. 2000. Sharp-shinned Hawk (Accipiter striatus). In The Birds of North America, No. 482 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Harrison, H. H. 1979. A field guide to western birds’ nests. Houghton Mifflin, Boston, MA.
Howell, S. N. G. and S. Webb. 1995. A guide to the birds of Mexico and northern Central America. Oxford University Press, New York.
Levad, R. 1998. Sharp-shinned Hawk (Accipiter striatus). In Colorado Breeding Bird Atlas, pp. 112-113 (H. E. Kingery, ed.), Colorado Bird Atlas Partnership, Denver. Lockwood, M. W. and B. Freeman. 2004. The TOS handbook of Texas birds. Texas A&M University Press, College Station.
Oberholser, H. C. 1974. The bird life of Texas, University of Texas Press, Austin.
Reinking, D. L. ed. 2004. Oklahoma Breeding Bird Atlas. University of Oklahoma Press, Norman.