Our Living Ki'SOurcTS — Binl\ 



67 



After the nationwide ban of DDT in 1972. 

 bald eagle reproduction improved and popula- 

 tions began increasing. In 1981 about 1,300 

 pairs nested in the United States outside Alaska. 

 The active protection of nesting habitat and 

 release of hand-reared eagles aided the popula- 

 tion increase. In 1993 at least 4,016 pairs of 

 bald eagles nested in the contiguous United 

 States, with an estimated additional 20.000- 

 25,000 pairs in Alaska. Bald eagles nesting 

 along the shorelines of Lakes Superior, 

 Michigan, Huron, and Erie have lower repro- 

 ductive rates and relatively high concentrations 

 of the toxic DDE and PCB compounds 

 (Bowerman 1993). Bald eagles nesting in 

 Maine also have low reproductive success. 

 probably because of environmental contami- 

 nants. 



Habitat loss remains a threat in many areas. 

 Historically there was a continuous (though 

 scattered) distribution of bald eagles in the 

 Southwest, south into Sonora and Baja 

 California, Mexico, where now only a remnant 

 population exists. Because population increases 

 were not unifomi throughout the range, the U.S. 

 Fish and Wildlife Service has proposed down- 

 listing this species from endangered to threat- 

 ened in certain geographic areas. 



Hawks 



Populations of sharp-shinned hawks 

 {Accipiter striatus) in the Midwest might be 

 increasing, but analyses of eastern hawk migra- 

 tion count stations reveal a drop in numbers of 

 juveniles, and blood samples collected from 

 sharp-shinned hawks in the Northeast contained 

 high DDE pesticide concentrations. Many other 

 factors could be involved in a population 

 decline, however. The sharp-shinned hawk pro- 

 vides an example of how monitoring can warn 

 researchers of a potential, long-term decline in 

 a regional population. 



Similarly, the northern goshawk (A. geiitilis) 

 counts of eastern migrants suggest a stable pop- 

 ulation, but analyses of counts from the West 

 reveal a decline. There is no widespread stan- 

 dardized design for surveying goshawks during 

 the breeding season. 



Habitat loss has reduced the number of 

 Harris" hawks (Parabiiteo unicinctus), whose 

 northern range extent is the southwestern 

 United States. Searches reveal that Harris" 

 hawks have been extirpated from some areas 

 such as the Colorado River Valley. California 

 and Arizona, and that clearing of brush for agri- 

 culture likely has led to more than 50% reduc- 

 tion in Texas in the winter. 



The biological status of the ferruginous hawk 

 {Buteo regalis) remains uncertain because it is 

 stable in some areas (e.g.. Great Plains), but 

 declining in other areas (e.g., half the western 



Table. Slatus and Irends ol raptors in tlie United .States. 



'Category 2 (C2)— Proposal to list is possibly appropriate but available data are not conclusive for threatened or endan- 

 gered status. 

 Category 3 (C3)— Proven more abundant or widespread than previously believed or not subject to identifiable threat. 



