
Breeding Population Indices - 
The very poor water conditions prevailing throughout the period of migra- 
tion and nesting is clearly reflected by the drastic decrease in numbers of ducks 
in the glaciated areas. (See Table II.) This is particularly significant when 
compared with the high populations of 1955, although it also represents a serious 
decline from the seven-year average. 
Results from the Flathead Valley Trend Area west of the Divide, where 
water conditions were excellent, indicated a 73 percent increase over 1955 in the 
number of breeding ducks. 
In the Southern unglaciated prairie, a complete count was again made on 
one trend area. Here the bulk of available water is contained in stock water 
reservoirs, and waterfowl density is low. This type of water area was little 
affected by the lack of precipitation in the early nesting season and there was a 
58 percent increase in duck numbers over 1955 and a 22 percent increase over 
the four-year average. . 
Table II - Waterfowl Popmilations as Determined fiom Aerial Census Routes 
Approximate Number of 
Size of Area Square Miles Sampled 
Physiographic Area (Square Miles) T 1955 1956 
Sheridan County 1,440 39 39 
Eastern Hi-Line 7,926 172 172 
Central Hi-Line 9,468 101 101 
Great Falls Piedmont 7,020 61 143 
Number of Ducks Per 
i _ ' ... Square Mile Population Estimate 
Physiographic Area 7-Yr. Ave. 1955 1956 1955 1956 
Sheridan County 29.5 41.4 26.6 £59,616 38, 304 
Eastern Hi-Line 5.3 6.4 4.6 50,688 36,432 
Central Hi-Line 11.3 15.0 7.5 142,020 71,010 
Great Falls Piedmont 9.7 5.2 4.6 36, 504 32,292 
Totals 288, 828 178,038 
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