State-dependent life history theory predicts a trade-off between an individual's state and reproductive effort. The identification and effects of key state variables, however, have not been explored empirically in depth. Although there are some studies which have provided evidence that state-dependent behaviour indeed occurs, the bulk of this work is neither experimental, nor related to reproduction. Furthermore, the quantitative effects of manipulations of specific state variables are invariably unknown (McNamara & Houston 1996). This thesis explores potential trade-offs between state and behaviour and determines if energy reserves can be employed as a useful state variable. In contrast to other empirical studies, parental states (energy reserve at dawn) were experimentally manipulated using a direct method, namely changes in overnight temperature (Warming, Chilling and Control). The effects of these temperature changes were quantified using indirect calorimetry. Responses to these experimental manipulations were measured by behavioural observations, a common method in behavioural ecology, but were also quantified in terms of energy expenditure, with the aid of the doubly labelled water technique. Thus, this thesis provides a unique quantitative approach, in that it measures both manipulations and responses in the currency of energy. Individual energy reserves at dawn significantly affected resource allocation decisions the subsequent day. Birds with surplus energy upon release increased the number of feeding visits to their nestlings whilst in parallel increasing energy expenditure. Those with an energy deficit at dawn, conversely decreased nest visitation rates along with energy expenditure. There were no effects of temperature manipulations upon mass or fatscore changes over the trial period, suggesting a regulation of somatic investment at a threshold level, whilst reproductive effort was varied depending on parental state. The responses to positive manipulations (warming) were congruent across two species with differing foraging ecologies: the swallow, an aerial feeder foraging in a variable environment; and the great tit, foraging in relatively stable woodland. Thus, the behavioural and energetic responses seen here were not the result of species-specific strategies. This points the way towards a general rule within state-dependent behaviour. The trade-off identified here implies that reproduction carries a cost, and that reproductive effort will be reduced if an animal's survival is jeopardized and vice versa: a life history response, mediated by an individual's body-state. Furthermore, the response of birds to positive and negative manipulations was large enough to be readily detected, even amongst the considerable variation in energy expenditure related to individual differences. This suggests that body-state not only plays a key role in allocation decisions, but that it is comparable in the scale of its effects to other major influences on energy expenditure of free-living animals.

A simulation matrix population model of a small population of wrens (Troglodytes troglodytes) is presented. The field work methods used to obtain and analyse the demographic rates are provided. This includes a description of the use of miniature radio tags to track juvenile (post-fledging) survival and dispersal, and capture mark recapture analysis of an eight year dataset to estimate adult survival rates, taking into account environmental variation and density dependence. Age related reproductive rates were obtained from detailed nest surveys. Using these demographic rates (means and variances), and information on density dependence in survival and breeding, a simulation matrix model was developed using Matlab (The MathWorks, Inc.). The operation of this model and its outputs are explained in detail, with particular reference to the methods employed to incorporate both density dependent survival and reproduction and environmental and demographic stochasticity. This model is then used to illustrate how, under plausible conditions of density dependence and stochasticity, large discrepancies are obtained between the deterministic, density independent elasticities of the population growth rate (λ) and the stochastic, density dependent elasticities of the equilibrium population size, extinction probability and invasion exponent. Since the elasticities of λ are often used to guide the management of endangered species, these results are particularly relevant to workers in the field of rare species conservation. While the importance of including environmental variation in the form of stochastic population simulations seems to now be generally accepted, the role of density dependent population regulation is still infrequently considered. Since one of the most common causes of population decline is habitat destruction, leading to an increase in population density within the remaining areas of habitat, this omission may rarely be justified. It is recommended that when elasticity analysis is conducted as part of species conservation efforts, both density dependence and stochasticity are included. Failure to do so may result in the misguided management of endangered species.

Thesis (M.A. (African Languages)) -- University of Limpopo, 2013 / Refer to the document

Recent declines in nesting success of some fish-eating seabirds in Alaska have been attributed to declines in availability of certain schooling forage fishes (e.g., capelin Mallotus villosus, Pacific sand lance Ammodytes hexapterus, and Pacific herring Clupea harengus pallasi). These fishes tend to have high lipid content compared with other species and, consequently, are assumed to have high nutritional value as food for young seabirds. I tested hypotheses that type of fish consumed by the nestling, and lipid:protein ratio of the diet constrain growth and development of piscivorous seabird nestlings. I raised seabird nestlings (Black-legged Kittiwakes, Rissa tridactyla and Tufted Puffins, Fratercula cirrhata) on controlled diets of either capelin, herring, or sand lance (high-lipid fish), or juvenile walleye pollock (Theragra chalcograma; a low-lipid fish). Seabird nestlings fed herring, sand lance, or capelin had higher growth rates (body mass and wing length) than nestlings fed equal biomass rations of pollock. Growth in body mass and wing length of kittiwake nestlings was not affected by lipid:protein ratio of the diet when on a high nutritional plane (i.e., high caloric intake), but growth was significantly affected by dietary lipid:protein ratio when on a low plane of nutrition. Growth in body mass and wing length of puffins was not significantly affected by the lipid:protein ratio of the diet. Diets with a higher lipid:protein ratio resulted in greater fat reserves in both seabird species, regardless of nutritional plane. Additionally, diets with a higher lipid:protein ratio resulted in higher apparent metabolizable energy coefficients. The increased growth rates, fat reserves, and energy utilization efficiencies of chicks fed high-lipid diets suggest that pre- and post-fledging survival are enhanced when parent seabirds have access to high-lipid forage fish. / Graduation date: 2000

Graduation date: 1948

Thesis (M.S.)--University of Montana, 2006. / Title from PDF t.p. (viewed on July 2, 2007). Includes bibliographical references.

Variable area surveys are used in large geographic regions to estimate the density of birds distributed over a region. If some birds go undetected, a measure of the effective area surveyed, the amount of area occupied by the birds detected, is needed. The effective area surveyed is determined by observational, biological, and environmental factors relating to detectability. It has been suggested that density estimates are inaccurate, and that it is risky to compare bird populations intraspecifically over time and space, since factors influencing bird counts will vary. There have been several controversial studies where variable area survey density estimates were evaluated using density estimates calculated from spot mapping as the standard for comparison. Spot mapping itself is an unproven estimator that the previously mentioned factors also influence. Without a known population density, determining how the different density estimators perform is difficult to access. Variable area surveys of inanimate objects whose densities were known have been conducted under controlled circumstances with results generally supporting the variable area survey method, but time and inability to control for all factors limit the application of this type of study. A simulation program that distributes over a region vegetation and a known density of birds, and then simulates the process of gathering bird detection data is one tool accessible to evaluate variable area density estimates. Within such a simulation study various observational, biological, and environment factors could be introduced. This thesis introduces such a simulation program, VABS, that was written with the objectives of identifying factors that influence bird counts and determining the limitations of the variable area survey. Within this thesis are discussions concerning the several factors that have been identified as influencing bird counts and the effects that these factors had on the Fourier series, exponential power series, and Cum-D density estimates when these factors were simulated in VABS. Critical assumptions of the variable area survey are identified, and the ability of the variable area survey to estimate density for different detectability curve is examined. Also included are discussions on the topics of pooling data gathered under different detectabilities and monitoring population trends. / Graduation date: 1994

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xv, 142 p. : ill., maps (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xiv, 156 p. : col. ill., maps (part col.). Includes abstract. Includes bibliographical references.

Thesis (Ph.D.)--Memorial University of Newfoundland, 2002. / Restricted until October 2003. Includes bibliographical references.