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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The importance of nesting cavities and brood habitat to wood duck production /

Robb, Joseph Russell, January 1986 (has links)
Thesis (M.S.)--Ohio State University, 1986. / Includes vita. Includes bibliographical references (leaves 105-110). Available online via OhioLINK's ETD Center.
2

Habitat use and productivity of harlequin ducks in the central Cascade Range of Oregon /

Bruner, Howard J. January 1900 (has links)
Thesis (M.S.)--Oregon State University, 1997. / Typescript (photocopy). Includes bibliographical references (leaves 42-44). Also available via the World Wide Web.
3

Population dynamics of ducks in Canada; the ratio of immatures to adults.

Wendt, John Stephen, Carleton University. Dissertation. Biology. January 1985 (has links)
Thesis (Ph. D.)--Carleton University, 1985. / Also available in electronic format on the Internet.
4

The role of interspecific competition in the decline of the black duck

Petrie, Mark Joseph, January 1998 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.
5

Tools for managing threatened species : improving the effectiveness of whio conservation : a thesis submitted for the degree of Doctor of Philosophy in Ecology at the University of Canterbury /

Whitehead, Amy. January 2009 (has links)
Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). Includes bibliographical references (p. 121-138). Also available via the World Wide Web.
6

The role of interspecific competition in the decline of the black duck /

Petrie, Mark Joseph, January 1998 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 1998. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.
7

Factors influencing breeding distributions of harlequin ducks, Histrionicus histrionicus, in northern Labrador : a multi-scale approach /

Heath, Joel P., January 2001 (has links)
Thesis (M.Sc.)--Memorial University of Newfoundland, 2002. / Restricted until May 2003. Includes bibliographical references.
8

Effects of aircraft disturbance on behaviour of harlequin ducks (Histrionicus histrionicus) /

Goudie, R. Ian, January 2004 (has links)
Thesis (Ph.D.)--Memorial University of Newfoundland, 2004. / Restricted until October 2005. Includes bibliographical references.
9

Hybridisation, and the Conservation of the Grey Duck in New Zealand

Muller, Wiebke January 2008 (has links)
Hybridisation is increasingly acknowledged as a conservation problem. The widespread hybridisation between grey duck (Anas superciliosa) and mallard (A. platyrhynchos) in New Zealand is a good example of a native species hybridising with a foreign one, and forms the main focus of this thesis. Mallards were introduced into New Zealand from Europe, and hybrids were soon observed. I surveyed the extent of the hybridisation on the West Coast of the South Island and found that, based on phenotype, at least half of population is now hybrids. Mallards and mallard-like hybrids dominate in the eastern South Island, while grey ducks occur only in some areas of the West Coast. Comparison with historical data suggests that the decline of the grey duck and the spread of hybrids has not stabilised and is ongoing. Contrary to expectations most grey ducks were found on agricultural land and most mallards on natural lakes or rivers, so grey ducks probably do not have an advantage over mallards on the less developed West Coast. An alternative theory is proposed here that explains the spatial distribution of hybridisation as a reflection of a temporal pattern. As mallards were first released in the east, the delay taken to cross the Southern Alps could also explain the pattern observed. This hypothesis suggests that the grey duck will persist in the southern West Coast. An analysis of the phenotypes of partners in pairs suggests that mating is positively assortative within each species and within hybrids. In fact, not a single pair of pure grey duck mated with pure mallard was observed in almost a thousand pairs, raising the question of how hybridisation started. There was a tendency for males to be more mallard-like in phenotype than their partners, suggesting there might be a selective advantage to the mallard male phenotype. This may be one factor explaining the dominance of mallards in the hybrid swarm. To analyse hybridisation at the genetic level, I analysed samples from grey ducks, mallards and domestic ducks with 11 microsatellite loci. This genotyping profile was then compared to ducks captured and shot in New Zealand. Genetic analysis confirms that the ducks in New Zealand were almost exclusively of hybrid origin. Phenotypic hybrid scores correlated with the established genotypic scores, but the correlation was imperfect, suggesting inaccuracies in either or both measures. As the spread of hybrids might be due to the differences in their fitness relative to either parent species, I compared the relative fitness of hybrid ducks using a range of health-related measures such as ecto- and endoparasite loads, immunocompetence, body condition, and heterophil to lymphocyte ratios. Overall, I found no conclusive evidence for any differences between grey duck-like and mallard-like individuals. However, as my sample consisted nearly entirely of hybrids, it is possible that fitness may differ from the parental species. To understand the outcome of hybridisation between two species, I next constructed a mathematical model to simulate hybridisation, and which allowed the specification of parameters describing mating patterns, differential survival, and differential reproductive output. The model successfully predicted the outcomes of two known hybridisation cases. In a sensitivity analysis for mallard and grey duck, the model predicted that this species pair is likely to hybridise under any set of conditions likely to be encountered across their shared range. Finally, in a study within the more general context of hybridisation, the influence of inbreeding on hybridisation rates was investigated using inbred and outbred lines of Drosophila species. I found evidence for increased hybridisation in inbred lines, and although further studies are needed to confirm the generality of this pattern, my results have implications for the management of hybridisation, and for the use of hybridisation as an adaptive strategy. In conclusion, my work suggests it is very likely that the grey duck will become extinct as a separate species in New Zealand in the near future, and that it is likely to be threatened in other areas of its range were it co-occurs with the mallard. The options for management of this situation are limited, as large areas without mallards are lacking. Captive breeding, or the management of grey duck populations on isolated islands appear the only feasible options. It seems unlikely that hybridisation can be reversed on the mainland, and a homogenous hybrid population is likely to eventually occupy the entire range of the grey duck across New Zealand.
10

Activity budgets and movements of black ducks (Anas rubripes) in Prince Edward Island.

Hickey, Thomas Earle. January 1980 (has links)
No description available.

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