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A Model of the Productivity of the Northern Pintail

Tables


Table 1.  Levels of parameters and variables in the sensitivity analysis of the northern pintail (Anas acuta) productivity model.
Parameter or variable name and levels Value Change from control (%)
Cropland to grassland ratioa
   Control 50:50  
   High 100:0

+100

   Low 0:100

-100

Semipermanent basins with water (%)
   Standardb

65.0

 
   High

87.0

+34

   Low

34.7

-47

Yearling (and adult) body weights (g)
   Standard

800 (900)

 
   High

860 (960)

+6.9

   Low

740 (840)

-6.9

Nest success (p)c
   Standard

0.135

 
   High

0.633

-80d

   Low

0.039

+80

Seasonal duckling survival rate for successful broods (p)c
   Standard

0.540

 
   High

0.810

+50

   Low

0.270

-50

Brood survival rate (p)c
   Standard

0.740

 
   High

0.920

+25

   Low

0.550

-25

a For the cropland to grassland ratio the control was a plot with a 1:1 ratio rather than the standard 1:0.57 ratio.
b Standard values that represent favorable waterfowl habitat in central North Dakota.
c Proportion = p.
d To vary nest success, daily nest mortality rates were adjusted by 80% in each habitat.

 

Table 2.   Habitat characteristics with which nesting of northern pintails at the Woodworth study area, Stutsman County, North Dakota, was simulated.
Habitat type Relative availability (%) Visual obstruction
measurement ranges (dm)a
Daily clutch
mortality ratesa
Cropland
   (fall-plow grain)
0.030 0.01-25.0 0.044-0.999
Planted cover 0.240 15.0-40.0 0.049
Planted cover (burned) 0.030 1.01-25.0 0.065-0.999
Grassland (nongrazed) 0.400 8.0-13.0 0.047
Grassland (burned) 0.080 0.01-13.0 0.047-0.999
Other 0.030 17.0-22.0 0.068
Wetland (temporary) 0.003(74)b 12.0-17.0 0.070
Wetland (seasonal) 0.061(49) 12.0-17.0 0.070
Wetland (semipermanent) 0.091(28) 12.0-17.0 0.070
Wetland (permanent) 0.035(0) 12.0-17.0 0.070
a Values change in response to phenological events or catastrophic events such as burning or plowing.
b Percentage of habitat available for nesting if <100 is placed in parentheses.

 

Table 3.  Definitions, values, and sources of estimates of parameters modified in the productivity model for northern pintails.
Parameter Definition Input value Source
H Hatch time of clutch (days)

31

Bellrose (1976)

INCTIME Incubation of clutch (days)

23

Bellrose (1976)

WTBAR(1) Average weight of arriving yearling female pintails (grams)

800

Bellrose (1976)

WTBAR(2) Average weight of arriving adult female pintails (grams)

900

Bellrose (1976)

CLUA Intercept in regression equation to calculate
   clutch size with average equal to 7.75 eggs
15.43

Bellrose (1976)

CLUB Slope in regression equation to calculate
   clutch size
0.063

Johnson et al.(1987)

ROBELA Slope in regression equation to calculate
   nest site selection attractiveness based on VOMs
   of available habitats
0.97

Calculated

ROBELB Intercept (see ROBELA) 0.28

Calculated

ROBLMIN Intercept (see ROBELA) 2.23 Calculated
LOSSLAY Weight lost per day during laying (grams) 7.5

Scaled from
   Johnson et al. (1987)

LOSSINC Weight lost per day during incubation (grams) 1.5 Scaled from
   Johnson et al. (1987)

 

Table 4.   Correlation coefficients (r2) of regressions of estimated nest initiations per pair (H careti) on percentages of all wetlands containing water in mid-May, mid-June, and average of May and June for northern pintails and mallards (Anas platyrhynchos) nesting in the Woodworth study area, North Dakota, 1966-81.
  Mid-May Mid-June Average
Species r 2 N a P b r 2 N P r 2 N P
Pintail 0.55 8 0.04 0.61 7 0.04 0.64 7 0.03
Mallard 0.30 7 0.20 0.69 6 0.04 0.49 6 0.12
a Number of years in the regression.
b Probability of a greater r2.

 

Table 5.  Changes in simulated recruitment rate from varying parameters and variables in the northern pintail productivity model.
Parameter or variable and
percent change from control
(%)a
Recruitment rate
Averageb SE Change (%)
Control 0.439 0.004  
Cropland to grassland ratio
   1:1 controlc 0.478 0.050  
   1:0 0.399 0.021 -16.5
   0:1 0.508 0.024 +6.2
Wetland condition
   +34 0.484 0.039 +10.2
   -47 0.251 0.011 -42.8
Yearling and adult body weight
   +6.9 0.519 0.027 +18.2
   -6.9 0.374 0.024 -14.8
Nest successd
    -80 1.347 0.016 +206.8
   +80 0.159 0.010 -63.8
Seasonal duckling survival rate for successful broods
   +50 0.647 0.011 +47.4
   -50 0.251 0.012 -42.8
Brood survival rate
   +25 0.553 0.027 +26.0
   -25 0.337 0.010 -23.2
a Controls were standard values that represent favorable waterfowl habitat in central North Dakota.
b N = 4 simulations.
c For cropland to grassland ratio the control ratio of 1:1 was used rather than the standard control ratio of 1:0.57.
d To vary nest success, daily clutch mortality rates were adjusted by ±80% in each habitat.

 

Table 6.  Main effects, two-way interactions, and three-way interactions (P = 0.0001) from a factorial analysis of variance of the sensitivity of recruitment rate in the northern pintail productivity model, ranked according to F value.
Parameter or variable F valuea Parameter variable F valuea
Nest success

100,000

Seasonal duckling survival rate × brood
   survival rate

3,102

Seasonal duckling survival rate

61,367

Nest success × seasonal duckling survival
   rate

40,510

Yearling and adult body weight × seasonal
   duckling survival rate

2,139

Brood survival rate

14,693

Nest success × seasonal duckling survival
   rate × brood survival rate

2,047

Wetland condition

10,032

Nest success × brood survival rate

9,846

Wetland condition × nest success ×
   seasonal duckling survival rate

1,732

Yearling and adult body weight

7,039

Wetland condition × nest success

5,323

Yearling and adult body weight × nest
   success × seasonal duckling survival rate

1,141

Yearling and adult body weight × nest
   success

3,753

Wetland condition × seasonal duckling
   survival rate

3,156

Cropland to grassland ratio

1,011

a 1 df.

 

Table 7.  Comparison between simulated and observed northern pintail productivity in the Woodworth study area, North Dakota, 1970-78 and 1981.
Source Wetland conditions Comparisons
N
Average
pairs
Average nest
initiations
Average
successful nests
Observed

Wet

3 36.0 20.3 9.3
Simulated

Wet

3 36.0 72.3a 12.3
Observed

Average

4 34.2 20.8 10.2
Simulated

Average

4 34.2 64.2a 10.5
Observed

Dry

3 17.0 11.7 4.0
Simulated

Dry

3 17.0 18.3 3.6
a Significantly different from observed data (P < 0.01).

 

Table 8.  Effect of simulated predator barrier fencing on northern pintail recruitment rates under wet, average, and dry wetland conditions at the Woodworth study area, North Dakota.
Wetland conditions Recruitment rate
Averagea SE Change (%)
Wet 0.701 0.022 +18.2
Average 0.624 0.036 +21.6
Dry 0.365 0.006 +15.5
a N = 4 simulations.

 

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