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Homing and Reproductive Habits of Mallards,
Gadwalls, and Blue-winged Teal

Results


Nesting

Nest Distribution. — On the Koenig study area we located 324 mallard, 316 gadwall, and 1,054 blue-winged teal nests useable for data analysis. Several of the cover types were represented by only 1 or 2 fields; thus, we were not able to test for duck nesting preferences. However, the large differences in duck nest densities calculated for the various cover types suggest strong hen selection for certain habitats. In 1976-78 before seeded nesting cover was available, odd areas had the highest mallard and gadwall nest densities (Table 4). Canal-side and roadside cover contained the next highest densities, and other cover types had low nest densities. Canal-side and odd areas also contained the highest blue-winged teal nest densities, but blue-winged teal also showed a preference for dry wetland.

Table 4.   Mallard, gadwall, and blue-winged teal nests per km2 in 8 cover types on the Koenig study area, North Dakota, 1976-78 compared to 1979-81.
Years and Species Pasture Hayland Roadside Canalside Dry wetland Seededa
cover
Odd
areas
Stubble
1976-78
Mallard 0.8 0.8 4.4 6.7 2.7   13.0 0
Gadwall 1.3 2.1 11.1 7.5 2.7   17.4 0
Blue-winged teal 6.2 8.8 12.2 40.3 30.1   26.1 0
Total 8.3 11.7 27.7 54.5 35.5   56.5 0
1979-81
Mallard 5.1 6.9 48.5 44.3 35.6 60.6 43.4 1.1
Gadwall 6.8 13.7 28.8 17.1 33.9 56.7 37.2 0
Blue-winged teal 26.2 38.9 100.0 117.1 140.7 67.3 54.9 0.4
Total 38.1 59.5 177.3 178.5 210.2 184.6 135.5 1.5
a No seeded cover was available in 1976-78.

In 1979-81, when seeded nesting cover became available, it ranked first in nest density ( = 58.7 nests/km2) for mallards and gadwalls. Odd areas, roadside, dry wetland, and canal-side had an average of 40.3, 38.7, 34.8, and 30.7 mallard and gadwall nests/km2, respectively. Other cover types had low rates of use. The highest blue-winged teal nest densities were in dry wetland, canal-side, and roadside. Pasture had low nest densities, but it was important as it composed the largest area of nesting habitat and contained the largest number of nests (also see Duebbert et al. 1986).

In a comparison between habitat and duck nest densities we found a significant relationship (r = 0.89, 5 df, P = 0.02) between mallard nest densities (Table 4) and visual obstruction rating (Table 1) and a less significant (r = 0.74, 5 df, P = 0.09) relationship between gadwall nest densities and visual obstruction rating. There was no significant correlation (r = 0.67, 5 df, P = 0.14) between blue-winged teal nest densities and the visual obstruction rating.

Nest Site Selection. — The average distance between nest sites based on previous breeding success and age groups was significantly different (F = 5.13; 2, 20 df; P = 0.02) among mallards but not for gadwalls (F = 1.79; 2, 23 df; P = 0.19) (Table 5). Pair-wise comparisons of the mallard data indicated that the average distance between nest sites in 2 successive years of unsuccessful ASY mallards was greater than that of successful ASY mallards. No differences in distances between SY mallards and either category of ASY mallards were detected.

Table 5.   Comparison of characteristics of the last nest sites used by breeding mallards and gadwalls in year 1 to the first nest site of the subsequent year and a comparison of the natal nest site characteristics with the first nest of female progeny on the Koenig study area, North Dakota, 1976-81.
Species and nest measurement Successful
ASY hens
Unsuccessful
ASY hens
First nest of female progeny
Mallard
n 8 5 10
(SE) distance (m) between nests 161 (61.6) 862 (316.4) 446 (90.1)
% in same cover type 100 80 60
% in same plant species 62 80 40
Gadwall
n 11 7 8
(SE) distance (m) between nests 249 (86.9) 831 (416.5) 699 (231.1)
% in same cover type 73 57 62
% in same plant species 54 43 25

There was no significant difference between the cover type of the last nest site of mallards ( = 4.19, 2 df, P = 0.12) and gadwalls ( = 0.50, 2 df, P = 0,78) in 1 year and that of the first nest site of the following year (Table 5). Similarly, there was no significant difference due to bell age or previous success in the plant species found at either successive mallard ( = 2.35, 2 df, P = 0.31) nest sites or at successive gadwall ( = 1.66, 2 df, P = 0.44) nest sites.

Mallard and gadwall hens may reuse nest bowls of previous years (Duebbert et al. 1983). However, none of the marked hens on either study area returned to a previously used nest bowl.

Nesting Success and Breeding Success. — Mallard and gadwall nesting success overall was 11 and 10%, respectively. Mallard and gadwall nest success was significantly different among years (F = 9,75; 3, 52 df; P < 0.001) but not among cover types (F = 0.75; 5, 52 df; P = 0.59). In 1978, the year after the 1977 drought, nest success at 27% for mallards and 30% for gadwalls was well above the 6-year averages. Blue-winged teal nest success (23%) was over twice as high as mallard and gadwall success and did not differ among years (F = 1.86; 3,14 df; P = 0.18) or cover types (F = 1.17; 5, 14 df; P = 0.37). Hen success rates for mallards and gadwalls were estimated at 25% using a relation developed by Cowardin and Johnson (1979, Fig. 5) for converting nest success data to hen success.

We found no significant difference ( = 0.16, 2 df, P = 0.92) in the number of fully feathered (Class III) mallard young produced by hens of different ages (Table 6) or the percent of hens that nested. Hen age influenced recruitment in gadwalls, and we found significantly fewer nests ( = 6.45, 2 df, P = 0.04) and young ( = 9.17, 3 df, P = 0.03) produced by SY hens compared to ASY and ATY hens. Yearling hens contributed little to recruitment, and 28 known-age SY hens produced an average of only 0.20 fully feathered young/ hen.

Table 6.   Age-related productivity of known-age resident mallard and gadwall hens on the Koenig and Woodworth study areas, North Dakota, 1976-81.
Species and age n Hens with a known nest No. of fully feathered younga No. of fully feathered young/hen
No. %
Mallard
   SY 41 27 66 59.4 1.45
   ASY 22 12 54 39.2 1.78
   ATY 11 5 45 13.0 1.18
Total or 74 44 59 111.6 1.51
Gadwall
   SY 28 10 36 5.7 0.20
   ASY 32 21 66 62.6 1.96
   ATY 54 33 61 87.5 1.62
Total or 114   64 56 155.8   1.37
a In several instances where we lost sight of the hen and brood before the young were fully feathered, we estimated the number of young that would have reached the fully feathered age class.

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