Conservation of migratory raptors: An overview based on fifty years of raptor banding

During the 50-year period 1931-80, 422,000 raptors were banded in the United States and Canada. Encounter rates were calculated, by decades of banding, for all birds reported outside of the l0-min block of latitude and longitude where they had been banded. Encounter rates for the various raptor species decreased from about 15-25% in the 1930s to about 1-5% in the 1970s. The percentage of encounters that were reported as shot also decreased sharply, from 55-85% for most species in the 1930s to 3-16% in the 1970s, reflecting the increase in protective state and federal legislation. During the same period the percentage of raptors found dead increased. In contrast, no such trends were apparent in raptors encountered south of the United States