Haliaeetus leucocephalus
This impressive bird, unmistakable in adult plumage, is the North American representative of the sea-eagles, a mostly Old World genus. Widespread and common when Europeans arrived, this eagle became the national bird of the United States in 1792, but did not achieve full protection until 1952 when a bounty in Alaska was abolished. By then the eggshell thinning effects of organochlorine insecticides were just becoming apparent. Restrictions on the use of these substances and widespread re-introduction campaigns have resulted in returning the Bald Eagle to many areas and its future seems much brighter than at its low point in the 1960s and 1970s (Oberholser 1874, Buehler 2000).
DISTRIBUTION. During the 1987-1992 field work seasons of the TBBA project, volunteers found 131 confirmed breeding records, mostly in the Coastal Prairies, southern Pineywoods and northern Coastal Sand Plain regions (see the region map in Lockwood and Freeman [2004]). The farthest north locations were along the Red River in quadrangles 33094, 33096 and 33097, with the most westerly near the intersection of the 30th parallel and the 98th meridian. The southernmost record was in quad 28097 near the coast.
Elsewhere Bald Eagles breed from central Alaska and the Aleutian Islands across Canada to Newfoundland and south in scattered locations across the 48 contiguous United States. Many eagles move south or to open water in winter months (Buehler 2000, Sauer et al. 2005). Young birds can disperse considerable distances; a bird banded in a nest on the Texas coast, was found as a breeding adult in Arizona (Lockwood and Freeman 2004).
SEASONAL CCURRENCE. Non-breeding and breeding populations show considerable overlap, both temporally and spatially. Bald Eagles arrive in Texas as early as August 6, with the largest population present from early October to late May. Breeding extends from late October to early May (occasionally to July), based on egg dated from November 6 to June 20 (Oberholser 1974, Lockwood and Freeman 2004).
BREEDING HABITAT. Bald Eagles breed in Texas from near sea level to about 1100 m (3600 ft; Oberholser 1974) in and around large aquatic environments (ocean coasts, reservoirs, large lakes and rivers, marshes and swamps). Here they scavenge or steal dead fish, or if necessary prey on dead or living birds, mammals or reptiles (Buehler 2000).
Most nests recorded in Oklahoma were along the Arkansas River (Jenkins 2004). Similarly in Colorado nearly 70% of breeding records came from riparian areas (Winternitz 1998) and in Arizona these birds nest near lakes, reservoirs and perennial rivers (Driscoll 2005).
Nests are immense piles of sticks, branches and human debris placed in the crown of a large tree or on an inaccessible cliff ledge. They may be used year after year or alternatively with another nest. More material is added each year so structures may reach 2.4-3 m (8-10 ft) across and sometimes fall of their own weight. Both sexes build the nest and line it with twigs, grass and moss. The female usually lays 2 (range 1-3) dull white eggs over 3-6 days. Incubation, mostly by the female, starts after the first egg is laid and continues for about 35 days. The young spend 8-14 weeks in the nest before attaining flight and then another 4-10 weeks with their parents (Harrison 1979, Buehler 2000).
STATUS. Bald Eagles once bred further west and north in Texas than they currently do. Oberholser’s (1974) map shows breeding locations in the northern Panhandle in Potter and Armstrong counties. TBBA observers and Patrikeev (2007) did not find Bald Eagles breeding in this area. Lockwood and Freeman (2004) report about 140 nesting pairs of Bald Eagles currently present in Texas.
Text by Robert C. Tweit (2007)
Literature cited.
American Ornithologists’ Union. 1998. Checklist of North American birds, 7th ed. Am, Ornithol. Union, Washington, DC.
Buehler, D. A. 2000. Bald Eagle (Haliaeetus leucocephalus). InThe Birds of North America, No. 506 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
Driscoll, J, T. 2005. Bald Eagle (Haliaeetus leucocephalus). In Arizona Breeding Bird Atlas. pp. 126-127 (T. E. Corman and C. Wise-Gervais, eds.), University of New Mexico Press, Albuquerque.
Jenkins, M. A. 2004. Bald Eagle (Haliaeetus leucocephalus). In Oklahoma Breeding Bird Atlas, pp. 90-91 (D. L. Reinking, ed.). University of Oklahoma Press, Norman.
Harrison, H. H. 1979. A field guide to western birds’ nests. Houghton Mifflin, Boston, MA.
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.
Patrikeev, M. 2007. Breeding birds of Lake Meredith National Recreation Area and Alibates Flint Quarries National Monument. Bull. Texas Ornithol. Soc. 40: 1-14.
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>
Winternitz, B. L. 1998. Bald Eagle (Haliaeetus leucocephalus). In Colorado Breeding Bird Atlas, pp. 108-109 (H. E. Kingery, ed.), Colorado Bird Atlas Partnership, Denver.