. The Canadian field-naturalist. 1980 ROLLEY AND KEITH: MOOSE. ROCHESTER, ALBERTA 11 present by assuming that they disappeared from the study area at the same rate as radio-collared Moose. The mean of the six estimates of observation effi- ciency (±SD) was (±). This was similar to the mean observation efficiency of on helicopter transects ( intervals) near Fort McMurray, Alberta (T. Hauge, personal communication). Le- Resche and Rausch (1974) also reported observation efficiencies of for experienced-current observers, under good to excellent conditions, when flyin
. The Canadian field-naturalist. 1980 ROLLEY AND KEITH: MOOSE. ROCHESTER, ALBERTA 11 present by assuming that they disappeared from the study area at the same rate as radio-collared Moose. The mean of the six estimates of observation effi- ciency (±SD) was (±). This was similar to the mean observation efficiency of on helicopter transects ( intervals) near Fort McMurray, Alberta (T. Hauge, personal communication). Le- Resche and Rausch (1974) also reported observation efficiencies of for experienced-current observers, under good to excellent conditions, when flying either transects or concentric squares over l-mi^ pens in fixed-wing aircraft. We used a mean observa- tion efficiency of in calculating densities from surveys on our study area. In 1975-76, two of three flights covered only the northern 67% of the survey area and one of two flights in 1976-77 covered just the northern 50%. We expanded these counts to the entire survey area for comparison with surveys conducted in previous years. It was first necessary, however, to correct for the uneven north-south distribution of Moose. During the winters of 1965-66 to 1974-75, 73% of the Moose were on the northern 67% of the study area, and 55% were on the northern 50%. The mean number of Moose observed on the two to six surveys per winter was divided by the observation efficiency of to obtain the average number of Moose present. Since 36% of the 179-km2 survey area has been cleared for agriculture, the 115-km- of remaining habitat was used to calculate mean density. Densities on the study area increased over 40-fold from a low of Moose/km^ of habitat in winter 1965-66 to Moose/km2 in 1978-79 (Figure 3). Mytton and Keith (unpublished data) reported to Moose/km2 in winters 1975-76 and 1976-77 just north of our survey area. These densities resemble the Moose/km2, post-fire, found by Peek (1974) in Minnesota. Evans et al. (1966) estimated Moose/ km^ on
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