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Food availability and selective utilization by juvenile mallards (Anas platyrhynchos platyrhynchos L.) on the Bear River Migratory Bird Refuge /Chura, Nicholas J. January 1962 (has links)
Thesis (Ph. D.)--Utah State University, Dept. of Wildlife Management, 1962. / Includes bibliographical references (leaves 84-91).
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Some aspects of wild mallard stocking on a large marsh habitat.Bailey, Robert Owen January 1974 (has links)
No description available.
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Nesting biology of wild and hand-reared mallards at Marshy Point, ManitobaGatti, Ronald Charles. January 1981 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
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Mallard population and harvest dynamics in WisconsinMarch, James Robert, January 1976 (has links)
Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 292-306).
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Food availability and selective utilization by juvenile mallards (Anas platyrhynchos platyrhynchos L.) on the Bear River Migratory Bird RefugeChura, Nicholas J. January 1900 (has links)
Thesis (Ph.D)--Utah State University, 1962. / Title from title screen (viewed Aug. 14, 2009). Department: Wildlife Management. Includes bibliographical references. Archival copy available in print.
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Some aspects of wild mallard stocking on a large marsh habitat.Bailey, Robert Owen January 1974 (has links)
No description available.
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Muscle oxygenation and blood flow during submersion in ducks (anas platyrhynchos) and seals (phoca vitulina) /Jöbsis, Paul D. January 1998 (has links)
Thesis (Ph. D.)--University of California, San Diego, 1998. / Vita. Includes bibliographical references.
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Synchronisation of communication systemsRamsay, Robert Duncan. January 1971 (has links) (PDF)
No description available.
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Hybridisation, and the Conservation of the Grey Duck in New ZealandMuller, 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.
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Synchronisation of communication systems.Ramsay, Robert Duncan. January 1971 (has links) (PDF)
Thesis (M.E.) -- University of Adelaide, Weapons Research Establishment, Salisbury & Dept. of Electrical Engineering, 1972.
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