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

Conclusions


1. ASY mallard and gadwall hens returned earlier in spring than did SY hens. Ten percent all mallard nests were initiated by 26 April, and there was no difference in the nest initiation dates for hen of different ages. The first 10% of gadwall nests were initiation dates for hen of different ages. The first 10% of gadwall nests were initiated by 20 May. Each increasingly older gadwall age class (SY, ASY, ATY) initiated nesting about a week earlier than younger hens.

2. Mallard and gadwall nest densities were highest in those cover types with the highest visual obstruction ratings, such as seeded nesting cover and odd areas. Blue-winged teal nest densities were highest in covers of moderate height that were widely distributed such as dry wetland, canal-side, and roadside.

3. Overall nesting success for mallards, gadwalls, and blue-winged teal was 11, 10, and 23%, respectively. Mallard and gadwall nesting success was different among years but not cover types. There was no difference in the number of fully feathered (Class III) young produced by mallard hens of different ages. SY gadwall hens were less productive than older hens producing only 0.20 fully feathered young/hen. Data collected in this study suggested that a portion of SY gadwall hens may not nest under certain conditions, such as in dry years.

4. Returning mallard hens that had nested successfully the previous year nested closer to the prior nest site than did unsuccessful mallard hens. Mallards and gadwalls that nested successfully 1 year and returned nested in the same cover type and plant species the next year.

5. An average of 52% of mallard and 61% of gadwall AHY hens that nested successfully in year t returned to the previous breeding site in year t + 1. An average of only 17% of mallard and 38% of gadwall AHY hens that nested unsuccessfully in year t returned in year t + 1. Return rates of ≥SY gadwalls increased as hens increased in age.

6. Few marked mallards or gadwalls became residents on the Koenig study area during the severe drought of 1977. Overall, the proportion of marked mallards that became residents was not related to May wetland conditions, but the percent of marked gadwalls that became residents was related to the number of wet basins in May.

7. Blue-winged teal AHY-hen return rates averaged only 4% and were not related to hen age and/or previous breeding success. In spring, blue-winged teal pairs apparently assembled on available wetland habitat.

8. Return rates of HY mallard and gadwall hens were both low (estimated at 29% for mallards and 9% for gadwalls). All HY mallards that returned to the study areas did so as yearling hens, but 5% of HY gadwall hens that returned did not do so until their third summer.

9. Clutch size declined 0.027 egg/day for mallards, 0.057 egg/day for gadwalls, and 0.058 egg/day for blue-winged teal as the nesting season advanced. Clutch sizes were similar between SY mallard hens and older hens and between SY blue-winged teal hens and older hens.

10. Survival rates of HY mallard and gadwall hens from hatching to near fledging were estimated at 0.681 and 0.828, respectively. The direct band recovery rate of yearling mallards was not different than that of older mallards. The direct band recovery rates of HY, SY, and ASY gadwalls decreased with each older age class.

11. Considering the hen success rate and survival rates of mallards on the Koenig study area, sufficient young were produced for the population to maintain itself. However, only about 45% of hens homed the next year—an insufficient number to maintain the breeding population. For the population to be self-sustaining, HY hens needed to home at higher rates than recorded in this study.


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