REASONS FOR CURRENT STATUS 



The peregrine falcon population decline almost 

 certainly resulted from a complex of environ- 

 mental factors, differing slightly from one area to 

 another (Hagar 1969; Herbert and Herbert 1969; 

 Hickey erf 1969). The population decline coincided 

 with the introduction and wide use of organo- 

 chlorine insecticides by 1967. The initial effect 

 was reproductive failure that wiped out the reserve 

 of nonbreeding individuals. 



The second stage was the steady numerical de- 

 cline in the 1950's of breeding adults in many re- 

 gions. DDE (a derivative of DDT) seems to have 

 been the chief chemical involved in the United 

 States (Hickey and Roelle 1969). 



The present total peregrine population in Utah 

 is believed to be only 10% of what it had been in 

 historic times; pesticide contamination and cli- 

 matic changes may have been major reasons for 

 the decline (Porter and White 1973). 



At least as early as 1948, DDE was present in 

 peregrine eggs in sufficient concentration to ac- 

 count for eggshell thinning, and is now considered 

 a major factor in their decline, with DDE levels of 

 15 parts per million in eggs that failed to hatch 

 (Peakall 1974, 1976). Contamination of birds and 

 eggs by persistent pesticides and the killing and 

 capture of birds on breeding grounds, in passage, 

 and on wintering grounds have been the main 

 causes of decline (King in press). 



Peregrines have continued to decrease since 

 1970 in most of their North American range, and 

 nowhere have they started to recover since reduc- 

 tion of DDT usage (Fyfe et al. 1976; Peakall 

 1976). 



PRIORITY INDEX 



10 



DESCRIPTION 



Peregrines are medium-sized hawk-like birds 

 with long, pointed wings and long tail. Wing-beats 

 are rapid and shallow. Adults are slate gray above, 

 with wing and tail feathers and flanks barred with 

 black, and black moustache marks on side of face. 

 The throat is white. Below is white and reddish 

 buffy, extensively spotted and barred with black. 

 Legs and feed are yellow. Immature birds are 

 brown above, streaked below. There are larger, 

 darker and black markings on face, more extensive 



than on the Arctic Peregrine falcon (F. p. tund- 

 rius); they are paler and more reddish, less grayish 

 below than F. p. pealei (White 1968; Fish and 

 Wildhfe Service 1973). 



Compared with tundrius, anatum is larger and 

 darker, bars on dorsal feathers more contrasting 

 with ground color; ventral surface more extensively 

 marked and washed with darker pinkish or rufous; 

 white auricular area less extensive in proportion 

 to black malar stripe (White 1968). 



Ground-color of the eggs varies from creamy 

 white to pale pink, almost always nearly or wholly 

 concealed by small blotches, spots or fine dots of 

 rich brown or reds sometimes concentrated at one 

 end. Measurements of 61 eggs, range 57 x 43, 

 56.5 X 43.5, 48.5 x 38.5 (average 52 x 41 mm) 

 (Bent 1938). 



RANGE 



This falcon formerly bred in all ecogeographic 

 regions of North America south of the Arctic 

 tundra, which is occupied by Falco peregrinus 

 tundrius, to northern Mexico; but excluding the 

 immediate vicinity of the northwest Pacific coast, 

 which is occupied by Falco peregrinus pealei, the 

 southeastern and Gulf of Mexico coastal plains, 

 and most of the Great Plains from Saskatchewan 

 and Manitoba south to Texas. It does not now 

 breed anywhere in the United States east of the 

 Rocky Mountains or in southeastern Canada 

 (Fyfe et al. 1976; Porter and White 1973; Cle- 

 ment ed 1974). 



RANGE MAP 



The breeding range shown (on the following 

 page) is taken from Fyfe et al. 1976). 



STATES/COUNTIES 



Colorado: El Paso, Boulder, Jefferson, 



Freemont, Montrose, Larimer 

 Archuleta, La Plata, Monte- 

 zuma, Moffat, Park, Mesa, 

 Garfield, Conejos, Douglas, 

 Pueblo (Bailey and Niedrach 

 1965;Enderson 1965). 



Wyoming: Teton, Yellowstone Park. 



Montana: Gallatin, Park, Sweet Grass, 



Stillwater, Cascade, Chouteau, 

 Fergus, Blain, Custer, Dawson, 



