Date of Award

4-24-1998

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

First Advisor

Richard D.|Svedarsky, W. Daniel Crawford

Abstract

A primary concern for wildlife managers is continued loss and modification of natural habitats and the resulting impacts on natural populations. If habitat alteration continues, more wildlife species will be using affected landscapes, and it will be increasingly important to understand wildlife biology in manipulated environments. I studied use of cultivated wild rice (Zizania palustris) paddies and associated habitats by waterfowl in northwest Minnesota (1993-1995) to evaluate their potential as migration, nesting, and brood-rearing habitat.I censused migrants using paddies during spring and fall and quantified availability of waterfowl food items collected from samples of paddy substrate. Eighteen species and 22.49 waterfowl per paddy hectare (ha) were recorded during peak migration and paddies averaged over 315 kg of quality forage per ha. Nutritional value of food items indicated paddies potentially provide over 3200 duck-use-days (DUDs) per ha.Breeding population counts and nest searches were used to determine size and composition of the local breeding population and nests were monitored to estimate nesting success and factors affecting it. I recorded 13 species during censusing and annual densities ranged from 1.43 to 2.61 breeding birds per paddy ha. A total of 443 waterfowl nests was discovered, with blue-winged teal (Anas discors), mallard (Anas platyrhynchos), and northern shoveler (Anas clypeata) comprising over 90% of waterfowl nests in upland habitats. Overall nest success was 19.9% and predators, primarily skunk (Mephitis mephitis), Franklin's ground squirrel (Spermophilus franklinii), and mink (Mustela vison), accounted for most unsuccessful nests.Mallard hens and ducklings were radio-marked and monitored to determine habitat use, home range size, and survival. Thirty-two hens and 77 ducklings (in 19 broods) were monitored and an estimated 42% of marked ducklings survived to fledge. All monitored broods used paddies during brood-rearing and home range sizes averaged 1.6 km$\sp2$. Paddy ditches were used extensively by broods of all ages, especially in early spring and late summer. Mink predation accounted for most duckling mortality after broods entered paddies.This wild rice-producing landscape provided habitat for migrating waterfowl and produced an estimated 97 fledged ducklings per 100 paddy ha.

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