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Effects of Grazing and Burning on Densities and
Habitats of Breeding Ducks in North Dakota

Tables


Table 1. Number of nests and initiation dates for waterfowl at Lostwood National Wildlife Refuge, North Dakota, 1980-88.

Species
Nestsa
n
Initiation dateb
Median
(90-percentile range)c
Mallard 881 7 May (20 Apr-3 Jun)
Gadwall 489 2 Jun (19 May-17 Jun
Blue-winged teal 435 24 May (11 May-14 Jun)
American wigeon 232 28 May (12 May-11 Jun
Lesser scaup 222 13 Jun (3 Jun-26 Jun)
Northern pintail 154 26 Apr (14 Jun-21 May)
Northern shoveler 91 17 May (4 May-6 Jun)
Green-winged teal 7d    
Canvasback 1d    
aTotal number of nests found; not all were used for analyses.
bEstimated date of nest initiation.
cMedian date of nest initiations and 90-percentile range in dates.
dInsufficient data to provide median or range.


Table 2. Mean values of annual nest density (nests/ha) of 7 species of waterfowl at Lostwood National Wildlife Refuge, North Dakota, 1980-88.

 
Mallard
Gadwall
Blue-winged
teal
Lesser
scaup
American
wigeon
Northern
shoveler
Northern
pintail
Treatment
Control 0.25 0.11 0.09 0.05 0.05 0.02 0.04
Spring graze 0.21 0.18 0.10 0.05 0.05 0.01 0.03
Spring burn 0.21 0.10 0.08 0.09 0.04 0.07 0.06
Summer burn/spring graze 0.17 0.13 0.13 0.06 0.05 0.02 0.02
Yeara
1980 0.36A 0.18 0.14 0.08 0.06BC 0.02 0.05
1981 0.40A 0.14 0.12 0.05 0.12A 0.03 0.07
1982 0.31A 0.12 0.09 0.04 0.08B 0.04 0.08
1983 0.17BC 0.06 0.10 0.02 0.06BC 0.01 0.03
1984 0.20B 0.11 0.10 0.05 0.04CD 0.01 0.02
1985 0.11BC 0.13 0.12 0.06 0.03CD 0.03 0.02
1986 0.09C 0.11 0.08 0.05 0.03CD 0.02 0.18
1987 0.16BC 0.12 0.11 0.06 0.05BCD 0.03 0.03
1988 0.08C 0.07 0.04 0.03 0.03D 0.01 0.01
aColumn means not sharing the same letter differ (P </= 0.05).


Table 3. Least-squares means of daily nest survival rate (DNSR) and Mayfield (%) estimate of nest success of 3 species of waterfowl at Lostwood National Wildlife Refuge, North Dakota, 1980-88.

 
Mallard
Gadwall
Blue-winged teal
DNSR
Mayfield
estimate
DNSR
Mayfield
estimate
DNSR
Mayfield
estimate
Average 0.970 34.5 0.977 44.7 0.966 31.3
Treatment
Control 0.967 31 0.981 51 0.955 20
Spring graze 0.961 25 0.974 40 0.966 30
Spring burn 0.974 40 0.950 17 0.958 22
Summer burn/spring graze 0.964 28 0.982 52 0.985 58
Yeara
1980 0.972A 37 0.982AB 53 0.984 58
1981 0.977A 44 0.971AB 35 0.965 30
1982 0.944BC 13 0.959AB 23 0.939 12
1983 0.961ABC 25 0.968AB 32 0.977 45
1984 0.969AB 33 0.972AB 36 0.971 36
1985 0.942BC 12 0.927B 7 0.952 19
1986 0.978A 50 0.983AB 56 0.973 40
1987 0.981A 51 0.990A 71 0.973 39
1988 0.966AB 30 0.984AB 56    
aColumn means not sharing the same letter differ (P </= 0.05).


Table 4. Proportions of duck nests found in vegetation types and availability of vegetation types at Lostwood National Wildlife Refuge, North Dakota in 1981 and 1987.

Year
Vegetation type
Available
Mallard
Gadwall
Blue-winged teal
1981
Brush 0.07 0.61 + 0.28 + 0b
Brush/grass 0.42 0.34 0.58 + 0.27
Grass/brush 0.16 0.02 - 0.02 - 0.31
Grass/forbs 0.27 0.01 - 0.04 - 0.37
Forbs 0.02 0 0.01 0.02
Shallow marsh emergent 0.05 0.02 - 0.06 0.03
1987
Brush 0.04 0.50 + 0.44 + 0b
Brush/grass 0.25 0.38 0.32 0.11 -
Grass/brush 0.44 0.11 - 0.11 - 0.49
Grass/forbs 0.21 0.01 - 0.07 - 0.19
Forbs 0.03 0 0.04 0.15
Shallow marsh emergent 0.03 0 0.04 0.06
a + indicates the habitat is preferred (P < 0.05); - indicates the habitat is avoided (P < 0.05).

bBrush was not tested for blue-winged teal. Because no nests were found in this vegetation type, it was not considered suitable nesting habitat for blue-winged teal.


Table 5. Proportions of duck nests found in vegetation types and availability of vegetation types at Lostwood National Wildlife Refuge, North Dakota, 1980-88.

Vegetation type
Availablea
American wigeon
Lesser scaup
Northern pintail
Northern shoveler
Brush 0.06 0.39 0 0.20 0.01
Brush/grass 0.33 0.56 0.32 0.60 0.21
Grass/brush 0.30 0.03 0.29 0.13 0.35
Grass/forbs 0.24 0.01 0.24 0.06 0.31
Forbs 0.02 0.01 0.02 0 0.02
Shallow marsh emergent 0.04 0.01 0.13 0.01 0.11
aAvailable vegetation is based on mean of 1981 and 1987 data.


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