. The Canadian field-naturalist. 1991 Savard and Lamothe: Abundance and Ecology of Scoters 489. Figure 1. Location of waterfowl survey areas in 1976. observers. Each sector was surveyed along series of parallel flight lines 4 to 10 km apart. Flight lines were followed until birds were spotted, then the heli- copter left the flight line to approach the birds so that they could be identified. Usually, the navigator made the identification and the two observers counted the birds. Following identification the flight line was resumed until other birds were detected. Transect width was not fixed but
. The Canadian field-naturalist. 1991 Savard and Lamothe: Abundance and Ecology of Scoters 489. Figure 1. Location of waterfowl survey areas in 1976. observers. Each sector was surveyed along series of parallel flight lines 4 to 10 km apart. Flight lines were followed until birds were spotted, then the heli- copter left the flight line to approach the birds so that they could be identified. Usually, the navigator made the identification and the two observers counted the birds. Following identification the flight line was resumed until other birds were detected. Transect width was not fixed but varied with weather and habitat, although we estimated that it averaged km. Most flights were conducted during calm weath- er. To complement transects, each of 24 randomly selected plots of km2, placed along transect lines in the Lake Bienville area, were thoroughly surveyed from the air. To estimate brood density, we combined the results of two surveys of the same transect lines, conducted three weeks apart (24-26 July 1976 and 16-24 August 1976). During each survey, broods were spotted and mapped and the number of young and their estimated age recorded (after Taber 1971), to determine whether or not broods were resighted. We assumed, from daily observations on some lakes that overland brood movements were negligible. Incubation was assumed to. last 30 days for both species of scoters (after Cramp and Simmons 1977). Brood behavior was studied on a small lake (Figure 1) which supported five scoter broods. Two broods were followed continuously during daylight hours for 2 days, using focal sampling (Altman 1974), and the behavior of the females and young was recorded as swimming, sleeping, preening (regrouped as resting for analysis), feeding, and watching (for female only). Because of frequent brood mixing the size of groups under observation ranged from 8 to 28 young. Results Over 95% of the birds seen from the air were identified. Scoters, with mergansers and Canada
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