The potential for competition between black ducks and mallards in Ontario / Marc Stewart Porter.
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TextPublication details: Guelph, ON : University of Guelph, 1993.Description: vi, 81 leaves : ill. , maps ; 28 cmOnline resources: Abstract: American black ducks (Anas rubripes) have declined over much of their breeding range in recent decades. To test between the confoudned effects of interspecific competition with mallards (A. platyrhynchos) and deforestation, I assessed black duck populations where mallards had appeared, but habitat remained unaltered. I also assessed potential competition between black ducks and mallards by measuring their relative use of dystrophic and highly eutrophic wetlands. Black duck abundance in forested northern Ontario was unchanged despite increased numbers of mallards, suggesting that habitat change may cause black duck declines.Black duck densities decreased, however, in forested southeastern Ontario where mallards and black ducks historically used similar wetlands. Forested habitat alone, therefore, may not ensure black duck persistence. Black ducks showed limited use of sewage enriched lagoons.Additionally, natural ponds had high levels of food relative to energetic requirements of res
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Thesis(M.Sc.)--University of Guelph, 1993.
Includes bibliographical references (leaves 71-81).
American black ducks (Anas rubripes) have declined over much of their breeding range in recent decades. To test between the confoudned effects of interspecific competition with mallards (A. platyrhynchos) and deforestation, I assessed black duck populations where mallards had appeared, but habitat remained unaltered. I also assessed potential competition between black ducks and mallards by measuring their relative use of dystrophic and highly eutrophic wetlands. Black duck abundance in forested northern Ontario was unchanged despite increased numbers of mallards, suggesting that habitat change may cause black duck declines.Black duck densities decreased, however, in forested southeastern Ontario where mallards and black ducks historically used similar wetlands. Forested habitat alone, therefore, may not ensure black duck persistence. Black ducks showed limited use of sewage enriched lagoons.Additionally, natural ponds had high levels of food relative to energetic requirements of res