-l 

4". 
io 
Fig. 6. Type 4 wetland (Shaw and Fredine 1956) in the Minnedosa study area, 
Pair Counts 
‘anvasbacks were counted from roadside 
transeets and within “beat-out” areas (waterfowl census 
technique. Stoudt 1971), Four or five roadside counts were 
made at about 10-day intervals, beginning the first week 
in May each year. These counts provided information on 
peak populations of breeding pairs. chronology of the nest- 
ing season, from ratios of drakes to pairs, and an indica- 
tion of success of early nesting hens. 
Beat-out counts of breeding pairs were made from 1963 
to 1966 on a 7.8-km? block study area, In 1967, these counts 
were extended to the 51.8-km* roadside transect system. 
Counts were conducted in mid-May and early June on all 
ponds within the block or transect. 
Reasonably accurate counts of breeding canvasbacks 
were obtained on the beat-out areas by counting all pairs 
airs of 
and lone drakes. Pairs plus lone drakes were used to 
calculate total pairs. Flocked drakes were assumed to have 
hens nesting outside the study area and were not counted. 
Lone hens were not counted on roadside census areas unless 
they had a nest; they usually represented less than 3% of 
the indicated pairs. Counts on beat-out areas along road- 
sides were not conducted during storms or when winds ex- 
ceeded 24 km/h. All counts were made between 0730 and 
1800 h and an attempt was made to include the same num- 
ber of morning and afternoon hours on each count. 
Nest Searches 
Canvasback nests were found by wading through stands 
of emergent vegetation. Searches were limited to wetlands 
that contained overwater nest cover of sufficient density 
