Buteo platypterus
This migratory hawk nests below the boreal forest from central Alberta to the east coast in Canada. Southward it nests largely east of the Great Plains throughout the eastern U. S. to the Gulf of Mexico with disjunct populations in Cuba and islands of the West Indies. Broad-wings winter in south Florida, the West Indies, and southwestern Mexico through Central America to Brazil and Bolivia (Am. Ornithol. Union 1998). They inhabit a wide range of deciduous and mixed forests, including wooded suburban areas, usually below 500 m (1700 ft) elevation. Numbers are stable in some eastern areas and slightly declining in others but increasing in the western range (Price et al. 1995, Goodrich et al. 1996, Sauer et al. 2005).
DISTRIBUTION: There are two nesting populations in Texas, both are of the subspecies B. p. platypterus. The larger eastern one is in lowland and upland forests, mostly east of the Trinity River. The other is further west, separated by Blackland Prairie, and ranges along the Balcones Escarpment between Travis and McLennan counties. The range broadens in the area of Parker, Tarrant, and Dallas counties north to Montague, Cooke, and Grayson counties (Pulich 1988, TBBA records, FRG). This central to north-central population is expanding.
Annually, in 1978-96, 1-3 nesting pairs of broad-wings were arranged linearly along about 11 km (7 mi) of Balcones Escarpment at Waco, McLennan County, and 2-3 more were within 25 km (16 mi) north and west of the city. Three rural territories averaged 30 ha (74 acres). Three within city limits averaged 6 ha (15 acres). Average densities were one nesting pair/5 km2 (2 mi2) in suburbia and 1/8 km(3 rni2) in rural habitat. The rural breeders are more sparsely distributed than those in the eastern U. S. but similar to others near the western limit of the range in Canada (Goodrich et al 1996).
Migratory flocks (kettles) containing over 1000 individuals are seen regularly in South, Gulf Coastal, and East Texas. They are among the largest anywhere in the U. S. (Palmer 1988). Single-day counts at one place have approached 250,000. Kettles in central and north-central Texas are less frequent and usually contain fewer individuals (Pulich 1988, FRG), although 1200 have been seen (Bush and Gehlbach 1978).
SEASONAL OCCURRENCE: Breeding individuals arrive March 9-April 15 (average March 31) in McLennan County, are building nests by April 7-24 (average April 12), and fledge young by May 30-July 6. These broad-wings arrive singly or in pairs before or coincident with the earliest kettles (FRG). Spring arrivals to the north are March 25-May 14 (Pulich 1988). Fall departures are August 2-October24 (average September 14) in McLennan County (FRG) and August 13-October 28 in north-central Texas (Pulich 1988).
BREEDING HABITAT: Many forest types are suitable, including late successional stages and selectively logged pines, provided that the environment is somewhat humid. Mixed pine-hardwoods, deciduous oak-hickory, elm-sugar- berry, and cottonwood-willow associations are occupied. Nests are in pines and deciduous and evergreen oaks (TBBA records, FRG).
McLennan County nests are along creeks, usually in ravines where trees average 580/ha (230/acre) and 12 m (40 ft) high, and the canopy coverage averages 96%. Nests are less than 500 m (1700 ft) from permanent water. less than 25 m (82 ft) from a forest opening. They are built at heights of 9-14 m (30-46 ft; Bush and Gehlbach 1978, FRG). Structurally and spatially, this habitat is similar to that in the eastern U. S. (Goodrich et at 1996).
STATUS: The species secretive nature while nesting contributes to the paucity of confirmed nesting records, so comparisons of historical with present data are difficult. Oberholser (1974) mapped just 4 nesting localities in the Texas eastern population, while the present survey (1987-1992) finds a total of 18 confirmed and probable sites. Oberholser mapped only one questionable nesting locality for the central/north-central population, whereas this survey confirms 5 and finds 13 altogether.
Broad-winged Hawks did not nest in central Texas historically (Strecker 1927) and rarely in north-central areas (Oberholser 1974; Pulich 1988). The first probable nesting pair in McLennan County was 1975, and a decade later this population had increased to at least 6 pairs spread over 36 km2 (14 mi2) north and west of the original locale (FRG.). There is no doubt that the Texas range has expanded in the last few decades, mostly westward, due to an increase in the central/north-central population.
Text by Frederick R. Gehlbach (1997)
Literature cited.
American Ornithologists’ Union. 1998. Checklist of North American birds, 7th ed. Am, Ornithol. Union, Washington, DC.
Bush, M. E. and F. R. Gehlbach. 1978. Broad-winged Hawk nest in central Texas: geographic record and novel aspects of reproduction. Bull. Texas Ornithol. Soc. 11: 41-43.
Goodrich, L. J., S. G. Crocoll and S. E. Senner. 1996. Broad-winged Hawk (Buteo platypterus).InThe Birds of North America, No. 218 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Oberholser, H. C. 1974. The bird life of Texas, University of Texas Press, Austin.
Palmer, R. S. 1988′ Handbook of North American birds, Vol. 5. Yale University Press, New Haven, CT.
Price, J., S. Droege, and A. Price. 1995. The summer atlas of North American birds. Academic Press, New York.
Pulich, W. M. 1988. The birds of north-central Texas. Texas A&M University Press, College Station.
Sauer, J. R., J. E. Hines, and J. Fallon. 2005. The North American Breeding Bird Survey, results and analysis 1966-2005. Version 6.2 2006. USGS Patuxent Wildlife Research Center, Laurel MD < http://www.mbr-pwrc.usgs.gov/bbs>
Strecker, J. K., Jr. 1927,. Notes on the ornithology of McLennan county, Texas. Spec. Bull. Baylor Univ. Mus. no.1.