Waterfowl Ecology an nagement

A primary concern for waterfowl managers is continued loss and modification of natural habitats and resulting effects on waterfowl populations. Thus it is increasingly important to understand use of manipulated environments. We studied the use by breeding dabbling ducks of cultivated wild rice (Zizania palustris) paddies and associated uplands in northwestern Minnesota during 1993-95. During 3 field seasons, we recorded an average of 1,196 (SE=285.9) breeding pairs (0.80 pairs/ha of wild rice paddy) on the study area. Mallards (Anasplatyrhynchos), blue-winged teal (Anas discors), and northern shovelers (Anas clypeata) comprised >950/o of the breeding population. We monitored 336 nests, and Mayfield's estimate of nesting success was 1 9.90/o (950/o C1 = 1 5.9-25.0%), with an average clutch size of 10.0 eggs (SE=0.13). We used nest success as a conservative estimate of hen success because we could not generate a reliable estimate of renesting rate from our data. Kaplan-Meier survival estimates for 70 radio-marked mallard ducklings from 19 broods was 42% (95% CI=25-58%). A production estimate from our 3,444-ha study area was 999 fledged ducklings/year (0.29/ha) and about 0.67 duckling/ha of wild rice paddy. Because wild rice production areas can attract and concentrate large numbers of breeding waterfowl, techniques that increase nest success and duckling survival (e.g., preserving large blocks of nesting cover, deploying secure nesting structures, and predator control) should be considered to maximize local production.