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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.
11

Uniparental incubation in a cool climate : behavioural adaptations in the Eurasian dotterel

Holt, Sue E. January 2002 (has links)
Energetic constraint during reproduction may limit the number or quality of young that a parent can produce per breeding attempt or the parent's longevity or future productivity, ultimately constraining lifetime reproductive success. The Eurasian dotterel Charadrius morinellus experienced energetic constraint during the Incubation period. Dotterel breed in the cold arctic-alpine zone and most breeding attempts are cared for by the male alone. The combination of a cold climate, giving high energetic costs of incubation and thermoregulation, and restricted foraging time due to uniparental Incubation, resulted in non-adaptive mass loss and constrained Investment of time and energy In incubation. If the incubation period is potentially energetically constrained, then behavioural mechanisms that reduce energetic costs could increase the production of young. When more energetically constrained, dotterel reduced the energetic cost of incubation by scheduling trips in conditions when the unattended eggs would have cooled more slowly and by making fewer, but longer trips. When suffering severe energetic constraint, some dotterel neglected their eggs for many hours: dotterel embryos' high chilling tolerance may have been necessary for successful uniparental incubation In a cold and unpredictable environment. Dotterel selected nest sites that allowed them to build larger nests with larger linings. Larger, better insulated nests probably decreased heat loss from the eggs and sitting parents, so reducing energetic costs during incubation. Sitting dotterel oriented into the wind, which probably reduced the disruption of their plumage and minimised their energetic expenditure on thermoregulation. In cooler conditions, dotterel changed their nest defence strategy and used energetically cheaper but probably riskier responses to simulated predators. Behaviours may be shaped under conflicting selective pressures and dotterel's management of their high energetic costs during the incubation period was constrained by egg-predation: dotterel's incubation scheduling appeared to be influenced by diurnal variation in the risk of predation and dotterel's nest defence behaviour traded-off energetic costs and the risk of predation. I declare that this thesis has been composed by myself and that it embodies the results of my own research. Where appropriate, I have acknowledged the nature and extent of work carried out in collaboration with others. This thesis presents data collected by myself over 2,212h spent in the alpine study areas from 288 days during my PhD field seasons in 1996,1997 and 1998. I also analyse some of Scottish Natural Heritage's dataset on dotterel biology collected between 1987 and 1999 by a team of fieldworkers, including myself (in Chapters 2,7 and 8).
12

The comparative physiological ecology of three submersed macrophytes

Titus, John Elliott, January 1900 (has links)
Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 188-195).
13

Aspects of foraging in black oystercatchers (Aves: Haematopodidae)

Groves, Sarah January 1982 (has links)
I studied foraging ecology of black oystercatchers (Haematopus bachmani) in the rocky intertidal. The aims of this study were: 1) to analyze prey choice and patch choice by adult black oystercatchers and evaluate how well their foraging performance was predicted by foraging theory; 2) to study development of foraging in young oystercatchers; 3) to indirectly examine the relationship between parental foraging performance and fitness by measuring chick growth and chick production. The following conclusions were reached: 1) Prey selection by oystercatchers was generally as predicted by theory, but birds showed partial preferences for prey. Patch choice followed general theoretical predictions, but profitabilities achieved within particular patch types were highly variable. Reasons for this are discussed. 2) Growth and physical maturation are important components in development of foraging. During the period of this study, chicks were heavily dependent on parental feeding, and the ability of chicks to forage independently developed after chicks left their natal area at about 50 days of age. 3) Chick growth varied between one-chick and two-chick broods, and this may be related to parental foraging performance. However, during this study chick production was constrained by weather and predation, and no relationship between parental foraging performance and fitness could be defined. / Science, Faculty of / Zoology, Department of / Graduate
14

Nutrient Effects on Autofragmentation of Myriophyllum Spicatum L.

Smith, Dian H. (Dian Helen) 08 1900 (has links)
A 2 x 2 factorial design investigated effects of sediment nitrogen and water potassium levels on autofragment production. Reduced nitrogen levels significantly increased autofragment production whereas potassium levels did not significantly alter production. Up to 50% of autofragment production abscised from parent plants grown under low nitrogen conditions compared to 12% or less under high nitrogen conditions.
15

The ecology of the aquatic macrophyte Myriophyllum spicatum L. /

Rivard, Paul Gordon. January 1984 (has links)
No description available.
16

Diet variability in Eurasian perch (Perca fluviatilis) as a response to environmental variables along a latitudinal gradient

Bublys, Kasparas January 2018 (has links)
Climate change is expected to have a profound impact on freshwater fish communities, especially at higher latitudes. In this study I investigated potential effects of climate change on the niche structure of Eurasian perch (Perca fluviatilis) by looking at their diet across a latitudinal gradient and at varying light climate. Dietary niche width of Eurasian perch did not differ significantly between boreal and temperate latitudes. Additionally, no significant difference in the prevalence of specialist individuals was found along the latitudinal gradient and water transparency levels. Habitat was the main factor that significantly affected niche width and level of specialization with both being significantly higher in the littoral habitat. Taken together my results suggest that climate change might indirectly affect niche patterns by altering fish densities through changes in productivity resulting in niche and specialization variation among habitats.
17

Modeling Eurasian watermilfoil (Myriophyllum spicatum) habitat with geographic information systems

Prince, Joby Michelle 30 April 2011 (has links)
Eurasian watermilfoil (Myriophyllum spicatum) habitat was predicted at multiple scales, including a lake, regional, and national level. This dissertation illustrates how habitat can be predicted for M. spicatum using publically-available data for both presence and environmental variables. Models were generated using statistical procedures and quantative methods to determine where the greatest likelihood of presence was located. For the single lake, presence and absence data were available, but the larger-scale models used presence-only methods of prediction. These models were paired with a Geographic Information System so that data could be visualized on a map. For the selected lake, Pend Oreille (Idaho), spatial analysis using general linear mixed models was used to show that depth and fetch could be used to predict habitat, although differences were seen in their importance between the littoral and pelagic zones. For the states of Minnesota and Wisconsin, Mahalanobis distance and maximum entropy methods were used to demonstrate that available habitat will not always mean presence of M. spicatum. The differing approaches to management in these states illustrated how an aggressive public education campaign can limit spread of M. spicatum, even when habitat is available. Bass habitat appeared to be the largest predictor of M. spicatum in Minnesota, although this was due to the similar environmental preferences by these species. Using maximum entropy, on a national level, presence of M. spicatum appeared to be best predicted by annual precipitation. Again, results showed that habitat is colonized as time permits, and not necessarily as conditions permit.
18

The ecology of the aquatic macrophyte Myriophyllum spicatum L. /

Rivard, Paul Gordon. January 1984 (has links)
No description available.
19

Eurasijská Ekonomická Unie: vývoj, problémy a perspektivy / Eurasian Economic Union: Development, Problems and Perspective

Prokhorov, Svyatoslav January 2019 (has links)
Title: Eurasian Economic Union: Development, Problems and Perspectives. The topic of the thesis is the Eurasian Economic Union (EEU) - a regional international law organization, established in 2015, which was granted with an international legal identity. The organization aim is not only to re-establish closer relations between the former Soviet Union states but also potentially to create a unified transnational cooperation in the Eurasian dimension. The EEU is very young organization, and still far from being a perfect one, that however deserves significant attention of the legal research. The aim of this research is to analyze the EEU system from the public international law perspective. Given the age of the EEU, the thesis is among the first in the Czech language environment dedicated to this organization. The thesis is divided into three parts. The first deals with the historical background that preceded the establishment of the EEU. The second part deals with the architecture of the EEU system, and is further divided into two subjects: the first deals with the analysis of the legal system of the EEU; the second focuses on the analysis of the functioning of the EEU bodies. The third part analyzes the current state of progress of the EEU in selected areas. Each chapter examines the various aspects...
20

Establishment and Competitive Ability of Nelumbo Lutea in Relation to Myriophyllum Spicatum

Snow, Joe R. 12 1900 (has links)
Limitations from reduced light and increasing water depth on Nelumbo lutea seedlings were determined in tank experiments. Survival was high in all tested light levels. Total biomass increased significantly with increasing light. Biomass allocation shifted significantly to root production between 3 and 6 weeks in the 10 and 24% levels. Survival decreased with increasing planting depth, and biomass of survivors reduced significantly between 0.5, 1.0, and 1.5 m depths. Nelumbo lutea and Myriophyllum spicatum populations were monitored for one season in a 0.7 ha pond to track changes in species dominance. Myriophyllum spicatum dominated early, and N. lutea dominated from July through October, suppressing M. spicatum at all depths. Competitive interactions between N. lutea and M. spicatum were investigated for two seasons in a container experiment situated within a pond. Where established, N. lutea dominated in the presence of M. spicatum. However, N. lutea could not be established in depths greater than 1 meter.

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