. The Canadian field-naturalist. 1969 Fyfe et al.: Pesticides in Prairie Falcons 193. Figure 1. Outline map of Saskatchewan and Alberta showing areas investigated. able degree of accuracy. The nest location is generally referred to as the eyrie or site (Enderson, 1964; Hickey, 1942; Webster, 1944), however, since the exact location of the eyrie or nest site may vary from year to year on a given cliff, or series of cliffs, we are using the term nesting territory to describe traditionally used nesting locations. Figures on populations and population changes are based on the number of occupied ne
. The Canadian field-naturalist. 1969 Fyfe et al.: Pesticides in Prairie Falcons 193. Figure 1. Outline map of Saskatchewan and Alberta showing areas investigated. able degree of accuracy. The nest location is generally referred to as the eyrie or site (Enderson, 1964; Hickey, 1942; Webster, 1944), however, since the exact location of the eyrie or nest site may vary from year to year on a given cliff, or series of cliffs, we are using the term nesting territory to describe traditionally used nesting locations. Figures on populations and population changes are based on the number of occupied nesting territories in each area (Table 1). For our purposes an occupied territory is defined as any previously known territory occupied by a pair of adult Prairie Falcons or any cliff defended by one or two adult Prairie Falcons at any time during the breeding season. Observations A. Populations Investigation in 1966 of prairie falcon nesting territories identified by Fyfe in 1958 and 1959 indicated that a sharp decline in the number of occupied territories had occurred in area B, with eight of nine former territories deserted. In sharp contrast, in area A six of seven 1958 and 1959 territories were occupied and one new territory was located. Area C was investigated for the first time in 1966, and 13 active territories were located. Field work carried out in areas A and C during the spring of 1967 indicated no change from the year before in the number of occupied territories. How- ever, although the number of territories remained the same, one nest in area A was deserted during incubation for no apparent reason. This nest originally. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Ottawa Field-Naturalists' Club. Ottawa, Ottawa Field-Naturalists' Club
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