OTHER CRITICAL ENVIRONMENTAL 

 REQUIREMENTS 



Freedom from human interference at nest 

 sites and lack of contamination of prey with 

 pesticide poisons (Hickey ed 1969; Herbert and 

 Herbert 1965; Clement ec? 1974). 



POPULATION NUMBERS AND TRENDS 



In the eastern U.S., before that population 

 started to decline, three Hudson River, New York, 

 peregrines attained minimal ages of 17, 18 and 20 

 years (Herbert and Herbert 1965). Data indicated 

 a low mortality rate, a strong tradition to reoc- 

 cupy stable nesting sites, a tenacity to remain in 

 face of human proximity if not molested, and a 

 nonbreeding segment that was generally capable 

 of supplying replacements (Hickey and Anderson 

 in Hickey ed 1969). Hickey (1942) estimated 19 

 pairs in about 25,900 sq km around New York 

 City. By 1952 R. A. Herbert and K. G. SkeUon 

 reported virtually 100% of pairs in Hudson Valley 

 had unsuccessful reproduction (Cade 1960). In 

 1947 that population had 9 breeding pairs ( a 

 peak number for the century) and productivity 

 averaged 1.1 to 1.2 young per nest in 1931-40, 

 and 0.75 in 1941-50. No young were reared in 

 1950. and production ceased in 1951. Breeding 

 pairs dropped to 7 in 1950, to 5 in 1952, to 4 

 in 1956 and none in 1961. Human disturbance, 

 including highway construction, taking of young 

 by falconers, shooting of adults, and unfavorable 

 weather contributed to extirpation of the popula- 

 tion (Herbert and Herbert 1969). 



In Massachusetts, reproduction seemed above 

 normal in 1946 but well below average in 1947 

 when broken eggs were observed for the first time. 



By 1951, occupation of eyries was spotty and by 

 1955-57 only an occasional single bird was left 

 (Hagar 1969). Complete failure of 14 pairs in 

 Massachusetts was attributed by Hagar {in Hickey 

 ed 1969, p. 32) to raccoon predation. 



In Pennsylvania, despite losses to hunters, fal- 

 coners and predators in 1946, there were still 17 

 active eyries which produced 1.25 young per nest 

 annually in the study area. From 1947 to 1952, 

 the number of active nests declined to 6 and pro- 

 ductivity per pair declined sharply. From 1953 to 

 1959 only 0.4 young were reared per pair per 

 year. The 3 pairs remaining in 1958 and one in 

 1959 reared no young despite lack of known dis- 



turbance (Rice 1969). 



On the upper Mississippi River in 1954 and 

 1955, the population was estimated at 1 pair to 

 30 km along one side of the river. These are now 

 gone. The last bird was seen in March 1964. Hu- 

 man disturbance did not seem to account for this 

 disappearance. The decrease seemed to progress 

 from south to north (Berger and Mueller 1969). 



By 1962, it was rumored that no young pere- 

 grines had been reared that spring in the north- 

 eastern states, and this situation was confirmed in 

 1964 when a survey team found no birds nesting 

 in 133 formerly used eyries in the eastern U.S. 

 The peregrine falcon now appears to be extinct as 

 a breeding bird in the eastern U.S. and south- 

 eastern Canada from the Mississippi Valley to the 

 Atlantic Coast and from Alabama north at least 

 to Nova Scotia, a region that previously contained 

 about 300 occupied nesting sites. However, cap- 

 tive-reared birds are being released there (Cade et 

 al. 1968,Fyfeet al. 1976). 



In the extreme northern part of the subspe- 

 cies' range within the boreal forest region of 

 Alaska, 200 to 250 pairs may have bred prior to 

 1950; less than 100 may remain (as of 1976). Per- 

 haps 400 to 500 pairs bred in the 1940 to 1950 

 period (Fyfe et al. 1976). Seventeen pairs were 

 found along 277 km of the upper Yukon River, 

 Alaska, in 1966, with an average linear distance 

 between occupied cliffs of 17 km (range 49 to 3 

 km). In 1951, average distance between 19 oc- 

 cupied cHffs was 15 km (range 50 to 3.5 km). On 

 the same stretch of river, L. B. Bishop (in Osgood 

 1900) estimated about 1 pair every 16 km, show- 

 ing quite similar density in the two periods and 

 demonstrating the usual static nature of peregrine 

 populations, each pair associated with a long-used 

 eyrie. It also showed that the population there 

 had not decreased as of 1966, even though levels 

 of chlorinated hydrocarbon chemicals were found 

 to be rather high in their eggs and tissues at that 

 time (Cade et al. 1968). As of 1969 White and 

 Cade (1977) found that populations along the 

 upper Yukon were still holding up rather well 

 with about 106 parts per milhon DDE in tissues, 

 while populations along the parallel Tanana River 

 to the south of it in Alaska with 334 ppm DDT in 

 1969 and 302 ppm in 1973 were pracrically gone. 

 Egg shells of Tanana River birds had thinned 

 about 17% by 1969 and 19.5% by 1973. Along 

 the Mackenzie River in northeast Canada (south 

 of the tree line), 18 known eyries were occupied 



