NPWRC :: A Model of the Productivity of the Northern Pintail

**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 ratio^a*
Control	50:50
High	100:0	+100
Low	0:100	-100
*Semipermanent basins with water (%)*
Standard^b	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	-80^d
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 rates^a
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 (_i) 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
Parameter or variable and percent change from control (%)^a	Average^b	SE	Change (%)
Control	0.439	0.004
*Cropland to grassland ratio*
1:1 control^c	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 success^d*
-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 value^a	Parameter variable	F value^a
Nest success	100,000	Seasonal duckling survival rate × brood survival rate	3,102
Seasonal duckling survival rate	61,367	Seasonal duckling survival rate × brood survival rate	3,102
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		2,047
Nest success × brood survival rate	9,846	Wetland condition × nest success × seasonal duckling survival rate	1,732
Yearling and adult body weight	7,039		1,732
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		1,141
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	72.3^a	12.3
Observed	Average	4	34.2	20.8	10.2
Simulated	Average	4	34.2	64.2^a	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).


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A Model of the Productivity of the Northern Pintail