Date of Award

1999

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Forestry, Wildlife, and Fisheries

First Advisor

Frank C. Rohwer

Abstract

Private landowners with regulated shooting areas (RSA) and the Maryland Department of Natural Resources (DNR) have released up to 120,000 hand-reared mallards (Anas platyrhynchos) a year. Duck harvest on Wildlife Management Areas (WMAs) included 30, 18, and 6 percent state mallards and 6, 10, and 4 percent RSA mallards in 1991, 1992, and 1993, respectively. Kaplan-Meier survival estimates for radio-marked mallards released on RSAs were 81--85% for mid-August to mid-October, but declined to 32.5% +/- 13.7 (95% C.I.) by the end of the hunting season in 1992 and 54.3% +/- 22.8% in 1993. Hunting accounted for 71% of all mortalities of RSA mallards in 1992 and 45% in 1993. Survival of DNR mallards at 7 weeks post-release was 23.0 10.6% and 28.4% +/- 17.8% for 1992 and 1993. Supplemental feeding of mallards released by DNR appeared to increase (P < 0.001) their survival to 7 weeks post-release (survival = 0.915 +/- 0.10). This result suggests that the low survival of mallards released by DNR was the result of energetic and/or nutritional deficiency. RSA mallards preferentially use the habitat on the RSA where they were released (P < 0.01). Characteristics of the source RSA affected the choice of property types used, although the source RSA was always among the most preferred types. Home range sizes and maximum distances moved from the release site were positively related to the size of the source RSA (P < 0.05). Mallards released on RSAs composed primarily of marsh habitats moved farther and had larger home ranges than those released on upland properties (P < 0.05). I recorded pair status and origin of 772 American black ducks (Anas rubripes) and 4,960 mallards in 1992 and 1993. Black ducks paired earlier than mallards, and wild mallards paired earlier than released captive-reared mallards. Pairing was highly assortative, only 3 of 229 female black ducks (1.3%) were paired with drake mallards. Three of 492 paired female mallards were paired with hybrid black duck x mallard males. In contrast, there were 8.4% hybrids among the black duck population based on hunter bag checks at WMAs. There was also assortative mating between wild and captive-reared mallards.

ISBN

9780599636422

Pages

126

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