NPWRC :: Mate Loss In Winter Affects Reproduction Of Mallards

**Table 1.** Means^a 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		SE	n		SE	n	F	df
Nest-initiation date	1996	10 May	1.25	25	10 May	1.31	24	0.01	1,46
Nest-initiation date	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
Egg mass (g), nest 1	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
Egg mass (g), nest 2	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
Clutch size, nest 1	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
Clutch size, nest 2	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
Egg fertility (%), nest 1	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
Egg fertility (%), nest 2	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
Viable eggs/clutch, nest 1	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
Viable eggs/clutch, nest 2	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
Days between nests	1997	7.70	0.56	10	9.00	0.41	4	1.93	1,12
^aLeast-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. ^bMain effects were not tested, because there was an interaction (P = 0.026) of winter body mass, male age, and treatment.

**Table 2.** Least-square means^a 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		SE	n		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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Mate Loss In Winter Affects Reproduction Of Mallards

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