
CENTRAL FLYWAY 
Breeding Population indices 
Aithough mid-May water area conditions were above normal, 
the numbe: of breeding ducks decreased. Water conditions prior to mid- 
May were poor. Thus the tow density of water areas that occurred during 
a large proport:on of the waterfowl migration apparently attracted less 
breeding ducks than in 1956, 
The 1957 State-wide breeding duck index was 5.34 ducks per 
square mile. The index was 30 percent below the 1956 index of 7.64 ducks 
per square mile, and 42 percent below the seven-year, 1950-56, average 
index of 9.26 ducks per square mile. 
The physiographic distribution of the breeding population 
appears in Tabie 2. 
Species composition of the breeding population as indicated 
by the numbex of males of each species observed on the ground transects 
appears in Table 3. Changes in composition from 1956 to 1957 were 
small. No change was indicated for blue~winged teal, gadwall, redhead, 
baldpate, canvas shack, BETS winged teal, and ringneck, Small increases 
occurred for the pinta:i (plus three percent) and scaup (plus three percent}, 
and small decreases occurred for the mallard ( minus one percent) and 
shoveler iminus four percent). 
Table 2 - Physiographic Distribution of the Breeding Waterfowl Population 
and 1956 to 1957 Trends = Part 1. 
Oe ed 








Uncorrected ok 
Physiographic Ducks Pez Sq.Mi. Corrected Ducks Per Sq. Mi. 
Division 1956 1957 1956 1957 #£Change 
Minnesota Valley 8.75 2.92 10.59 3.78 - 64% 
Prairie Hilts 13.71 8.40 16.58 10.84 - 35% 
James River Valley 7,89 4,71 9.55 6.08 - 36% 
Missouri Hills 7.27 6,38 8.80 8.23 ~ 6% 
Missouri Plateau 3.79 2.60 4,58 3.35 - 27% 
State-wide Total 6,31 4.14 7,64 — 5.34 ~ 30% 

* Corrected from ground transect data (Hast-River, exclusively) to compen- 
sate for unobserved females on nests, Corrected by 1.21 in 1956 and 1.29 
in 1957. 57 
