66 



Bird.\ — Our Living Rf sources 



Northern goshawk {Accipiter gen- 

 lilis) in adult plumage, is an exam- 

 ple of a raptor species for which 

 there is concern about status. 



birds, reptiles, amphibians, and insects. 

 Ciianges in raptor status also can be indicators 

 of more subtle detrimental environmental 

 changes such as chemical contamination and 

 the occunence of toxic levels of heavy metals 

 (e.g., mercury, lead). Consequently, determin- 

 ing and monitoring the population status of rap- 

 tors are necessary steps in the wise management 

 of our natural resources. 



Methods 



We did not compile summary statistics or 

 analyze data for any species: rather, we only 

 have summarized the interpretations and analy- 

 ses of others. Our summary of raptor status 

 draws largely on the biological literature and on 

 state and federal government reports. Much of 

 this information is summarized in Johnsgard 

 ( l%8). Palmer (1988), and White (1994) and in 

 proceedings sponsored by the National Wildlife 

 Federation (NWF 1988. 1989a, 1989b, 1990. 

 1991). Other information is from unpublished 

 data (S.W. Hoffman, HawkWatch International; 

 J.C. Bednarz, Arkansas State University: and 

 W.R. DeRagon, U.S. Army Corps of 

 Engineers). 



Interpretations and analyses to determine 

 raptor status and trends can be characterized in 

 four general types: impressions of biologists 

 and of other serious observers of wildlife; 

 impressions or nonstatistical analyses of orga- 

 nized searches or of tallies of birds seen (e.g., 

 Christmas Bird Counts): statistical analyses of 

 intensive quantitative status surveys; and statis- 

 tical analyses of standardized counts, incorpo- 

 rating estimates of the survey effort (e.g., num- 

 ber of persons, time expended, area covered). 



Our conclusion about the status of each 

 species (Table) is usually applied on a nation- 

 wide scale, but often must be qualified because 

 of local or regional concerns. These reflect 



habitat modification or contamination for which 

 we did not have information on a broader scale. 

 We used statistical results when available, but 

 usually our conclusions are based on impres- 

 sions or qualitative analyses because only that is 

 available on a scale across the species" range, or 

 the United States. 



Selected Species 



Ospreys 



Nesting ospreys (Paiidion haliaetus) are con- 

 centrated along the Atlantic coast. Great Lakes, 

 the northern Rocky Mountains, and in the 

 Pacific Northwest. Most regional populations 

 declined through the early 197(J"s, but the mag- 

 nitude of decline varied, with the North Atlantic 

 coast and Great Lakes being most severe. After 

 the 1972 nationwide ban of the insecticide DDT, 

 raptor productivity improved and population 

 numbers increased in most areas. Ospreys also 

 benefited from reservoir construction, especially 

 in the West. Osprey numbers generally are sta- 

 ble, but in some areas they are still increasing. 

 The large stick nests of ospreys, like those of 

 bald eagles (Huliaeetus leiicoccpluilus), are rel- 

 atively conspicuous, thus aiding counts of occu- 

 pied nests, which are used as a measure of pop- 

 ulation size. Counts from most states in the early 

 1980's provided an estimate of about 8,000 nest- 

 ing pairs. Also, because several osprey popula- 

 tions were studied for many years, a general 

 knowledge of their population dynamics permits 

 a greater understanding of this species" status. 



Snail Kite 



The endangered snail kite (Rostrhamiis 

 sociabilis) breeds in central and southern 

 Florida, the northern extent of the species' 

 range, where it is associated with wetlands that 

 are affected by management of water levels. 

 From 1900 to 1960 the population declined; 

 however, it then increased, and now remains 

 stable with fluctuations from 300 to 800 birds 

 (R.E. Bennetts. University of Florida, personal 

 communication). 



Bald Eagles 



Many local bald eagle populations showed 

 sharp declines (25% toloO'/f ) from 1950 to the 

 1970"s. Populations were adversely affected by 

 shooting, habitat destruction, and organochlo- 

 rine pesticides (primarily DDT). The bird was 

 protected by the Bald Eagle Protection Act of 

 1940. In 1978 it was reclassified as endangered 

 in 43 states and threatened in 5. With the docu- 

 mented effects of DDT on reproduction, early 

 studies emphasized locating breeding pairs and 

 monitoring reproductive success. 



