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Mate Loss In Winter Affects Reproduction Of Mallards

Tables


Table 1. Meansa of reproductive variables for captive, wild-strain, yearling female mallards that were widowed in winter and allowed to pair again (treatment group) or allowed to maintain pair bonds during winter (control) at Delta Waterfowl and Wetlands Research Station, Manitoba, Canada, 1996-97.
      Widow Control    
Variable Year mean of x SE n mean of x SE n F df
Nest-initiation date 1996 10 May 1.25 25 10 May 1.31 24 0.01 1,46
1997 21 May 1.47 27 23 May 1.67 25 1.41 1,50
Egg mass (g), nest 1 1996 54.40 0.62 23 53.60 0.90 22 0.53 1,43
1997 52.94 0.90 26 53.43 0.84 25 0.22 1,48
Egg mass (g), nest 2 1996 54.74 1.11 11 54.63 1.25 9 0.01 1,16
1997 53.23 1.52 10 57.50 2.40 4 2.25 1,12
Clutch size, nest 1 1996 10.49 0.88 17 11.81 0.86 18 1.14 1,32
1997 8.57 0.54 23 10.48 0.52 25 6.52 1,46
Clutch size, nest 2 1996 8.45 0.93 11 7.88 0.72 8 0.29 1,16
1997 7.70 0.65 10 9.50 0.50 4 2.70 1,12
Egg fertility (%), nest 1 1996 63.62 8.27 21 58.87 8.38 21 0.16 1,39
1997 77.70 7.41 25 59.75 7.41 25 2.93 1,47
Egg fertility (%), nest 2 1996 50.52 14.82 11 65.00 15.58 8 b b
1997 52.38 14.38 10 78.89 9.97 4 0.77 1,11
Viable eggs/clutch, nest 1 1996 7.35 1.02 17 6.45 0.99 18 0.39 1,31
1997 6.83 0.93 23 6.27 0.89 25 0.19 1,45
Viable eggs/clutch, nest 2 1996 4.31 1.18 11 4.87 1.40 8 0.01 1,15
1997 3.50 0.95 10 7.25 1.49 4 0.34 1,12
Days between nests 1996 15.55 0.65 11 14.33 0.82 9 0.34 1,16
1997 7.70 0.56 10 9.00 0.41 4 1.93 1,12
a Least-square means for nest-initiation date, 1996; clutch size of nest 1, 1996-97; egg fertility of nest 1, 1996-97 and nest 2, 1996; and number of viable eggs in clutch 1 and clutch 2, 1996-97. Least-square means adjusted for ≥ 1 significant (P ≤ 0.05) independent variables revealed by analysis of covariance; other means were not adjusted.
b Main effects were not tested, because there was an interaction (P = 0.026) of winter body mass, male age, and treatment.

 

Table 2. Least-square meansa for date of nest initiation, egg fertility, and viable eggs for captive, wild-strain, yearling female mallards paired with yearling or 2-year-old males at Delta Waterfowl and Wetlands Research Station, Manitoba, Canada, 1996.
   Yearling male mate 2-year-old mate    
Variable mean of x SE n mean of x SE n F df
Nest-initiation date 12 May 1.17 28 8 May 1.35 21 6.09 1,47
Egg fertility (%), nest 1 41.95 7.65 24 80.61 8.83 18 10.95 1,40
Viable eggs, nest 1 4.69 0.97 18 9.09 1.00 17 9.87 1,32
Viable eggs, nest 2 2.00 1.34 8 7.09 1.14 11 8.33 1,17
a Least-square means adjusted for ≥ 1 significant (p ≤ 0.05) independent variable as revealed by analysis of covariance.

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