A Historical Review of Peregrine Falcon Breeding and Summering Records for Arizona and the Navajo Indian Reservation

Attributes of a Breeding Population of Peregrine Falcons Associated with Reservoirs on the Colorado River

“…Historical Context. The first known peregrine breeding territory within LMNRA was discovered in 1985, corresponding roughly with the discovery of large numbers of breeding pairs upriver in the Grand Canyon (Ellis andMonson 1989, Brown et al 1992). The patchy nature of available nesting cliffs and extensive areas of open surface water found in LMNRA provide an interesting contrast to the near continuous presence of suitable peregrine nesting habitat found in the Grand Canyon, where tight canyon walls overlook the swift waters of the Colorado River and large terraced cliffs rise up to 1.5 km above the river (Brown et al 1992).…”

“…Peregrine Falcons (Falco peregrinus) were not known to breed in large numbers along the Arizona, Nevada, and California portions of the Colorado River prior to the latter half of the twentieth century (Bond 1946, Ellis andMonson 1989), although details of that time are poorly known. The lack of breeding records is somewhat surprising, considering the abundance of suitable nest cliffs, although few formal studies were conducted in the region before 1975 (Ellis and Monson 1989).…”

“…Peregrine Falcons (Falco peregrinus) were not known to breed in large numbers along the Arizona, Nevada, and California portions of the Colorado River prior to the latter half of the twentieth century (Bond 1946, Ellis andMonson 1989), although details of that time are poorly known. The lack of breeding records is somewhat surprising, considering the abundance of suitable nest cliffs, although few formal studies were conducted in the region before 1975 (Ellis and Monson 1989). Grinnell (1914) did not record peregrines along the lower Colorado River from southern Nevada to the Mexico border during a zoological expedition in 1910, nor did Bond (1946) cite evidence of them breeding upriver in the Grand Canyon during his western North American species assessment.…”

“…Grinnell (1914) did not record peregrines along the lower Colorado River from southern Nevada to the Mexico border during a zoological expedition in 1910, nor did Bond (1946) cite evidence of them breeding upriver in the Grand Canyon during his western North American species assessment. A historical review by Ellis and Monson (1989) indicated there may have been four breeding sites along the lower Colorado River below the Grand Canyon before 1975, with six more probable breeding sites throughout northern Arizona. Ellis and Monson (1989) documented 41 confirmed or probable breeding sites throughout Arizona during surveys from 1975-1985, and they did not detect peregrines breeding downriver below the Grand Canyon.…”

“…A historical review by Ellis and Monson (1989) indicated there may have been four breeding sites along the lower Colorado River below the Grand Canyon before 1975, with six more probable breeding sites throughout northern Arizona. Ellis and Monson (1989) documented 41 confirmed or probable breeding sites throughout Arizona during surveys from 1975-1985, and they did not detect peregrines breeding downriver below the Grand Canyon. Correspondingly, little was known about peregrines in Nevada; only five breeding pairs were known throughout the state before the mid-1950s, after which they were thought to be extirpated statewide as a breeding species (Alcorn 1988).…”