In this study, I first describe distribution and abundance of breeding Eared Grebes {Podiceps nigricollis) in British Columbia. Second, I characterize and examine the relationships between nesting habitat and nest site selection on breeding group size. Finally, I. examine effects of colony size, nesting chronology and nesting synchrony on reproductive success at Eared Grebe colonies. I surveyed 421 wetlands in 1985 and 1986 and located 47 lakes used by nesting Eared Grebes. Those 47 lakes accomodated from a low estimate of 1761 to a high estimate of 4474 pairs. Breeding abundance, calculated from adult, nest and young counts, ranged from single pairs to more than 590 pairs per lake. Breeding took place in shallow lakes of various sizes, subject to extensive variations in water levels. Breeding abundance was positively correlated with lake area. Fewer breeding pairs utilized nesting areas close to shore (in shallower water) than nesting areas far from shore (in deeper waters). Nesting areas close to shore were found in smaller lakes and were used less often in consecutive years than nesting areas far from shore, presumably because of lower habitat predictability. An experiment with unattended artificial nests showed that nest predation was higher far from shore than close to shore. Nesting areas close to shore were used by small groups. These maximized concealment by being located in denser vegetation. Nesting areas far from shore were used by larger groups and were located in more open areas. On both years, adults arrived at nesting lakes in April and May, started laying on 27 May and departed from, nesting areas in late July and- early August. Nesting was significantly earlier and reproductive success per pair was significantly higher in 1985 than in 1986. A .stepwise multiple regression examined effects of colony-size, synchrony and chronology on nesting success. Only nesting chronology accounted for differences in nesting success. Late nesters were not birds attempting to renest. Instead, there appeared to be qualitative differences across colonies that were related to ages of breeders. Eared Grebe colonies are likely not formed from passive aggregation at limiting resources and there are likely no foraging benefits from colonial nesting. Nesting colonies could increase detection and mobbing of predators, but no evidence supported this. Anti-predator benefits of coloniality might have been masked by differences in breeding chronology and synchrony, or were missed because of low sample size. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Wetlands are some of the most diverse and productive ecosystems on earth. Water-level fluctuations determine the ecological function of shallow lakes and wetlands. Currently, anthropogenic modification to water-level fluctuations is the leading source of ecological degradation in lake and wetland ecosystems worldwide. I used wading birds nesting in Lake Okeechobee, as a model system to address the challenges of environmental restoration within an ecosystem greatly impacted by anthropogenic activities. Specifically, I 1) identified environmental factors most important for predicting the number of wading bird nests, 2) tested the assumptions of both the match-mismatch and the threshold hypothesis by modeling the relationship between nesting success and prey density with foraging habitat availability, and 3) measured the stress response of Great (Ardea alba) and Snowy Egrets (Egretta thula) to hydrologically-mediated changes in food availability. Collectively, the results suggest that the number of nests was greatest when area of nesting substrate was high and water-levels were moderate (3.9 - 4.4 m). Nest numbers dropped when either nesting substrate or foraging habitat was limited. My investigation into the predictions of the match-mismatch and threshold hypotheses found that indeed, prey density can reduce or intensify the effects of a mismatch event. The interaction of prey density and foraging habitat availability was significant and positive in both models. Saturation thresholds existed for both fledging success (147 prey (m^2)^-1) and total productivity (189 prey (m^2)^-1), above which high concentrations of prey could sustain nesting when foraging habitat availability was low. Finally, my studies of the stress response support the hypothesis that hydrologic factors associated with prey availability play an important role in regulating nesting patterns, although the level of food limitation the birds experience at the lake was not as severe as expected. Model selection identified foraging habitat availability as most influential to the nestling Great Egret stress response, whereas foraging habitat availability and prey density both influenced nestling Snowy Egret stress response. Moreover, the Snowy Egret stress response was more sensitive to changes in prey availability than was the Great Egret stress response. Temperature and foraging conditions influenced yolk corticosterone concentrations for both egret species. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph.D.)--Montana State University--Bozeman, 2007. / Typescript. Chairperson, Graduate Committee: Andrew Hansen. Includes bibliographical references.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Seasonal variation in food availability is one of the primary limitations to avian populations, particularly during the breeding season. However, the behavioral responses between species may differ based on foraging strategies. I examined the influence of food availability on landscape-level habitat selection, patch-level habitat selection, and movements of two wading bird species with divergent foraging strategies, the Great Egret and White Ibis. On a landscape scale, there appeared to be a relationship among resource availability, the temporal scale of the independent variable, and whether the response was similar or different between species. At the patch level, results demonstrated a relationship between resource availability and the spatial scale of the independent variables selected by birds. Species movements were consistent with the differing strategies. This study is the first to make the link between landscape hydrology patterns, prey availability, and responses in wading bird habitat selection at multiple spatial scales. / by James M. Beerens. / Thesis (M.S.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.

Successful foraging by avian predators is influenced largely by prey availability. In a large-scale experiment at the Loxahatchee Impoundment Landscape Assessment project within the Arthur R. Marshall Loxahatchee National Wildlife Refuge, I manipulated two components of prey availability, water depth and vegetation density (submerged aquatic vegetation and emergent vegetation), and quantified the response by wading birds in terms of foraging habitat selection and foraging success. Manly's standardized selection index showed that birds preferred shallow water and intermediate vegetation densities. However, the treatments had little effect on either individual capture rate or efficiency. This was a consistent pattern seen across multiple experiments. Birds selected for certain habitat features but accrued little benefit in terms of foraging success. I hypothesize that birds selected sites with shallow water and intermediate vegetation densities because they anticipated higher prey densities, but they did not experience it here because I controlled for prey density. / by Samantha Lantz. / Thesis (M.S.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.

In the Sumberjaya district of West Lampung, Indonesia, there has been widespread replacement of rainforest by robusta coffee. However, few studies have explored the relationship between birds and coffee gardens in Southeast Asia. This study examines the use of coffee gardens and other habitats by birds in the Sumberjaya and Pesisir regions. Birds and their habitat use were surveyed, as were structural and floristic vegetation features. Interviews with farmers indicated land management practices and limitations, as well as local perceptions of shade trees, birds and conservation programs. There were clear differences in bird diversity and assemblage uniqueness between types of coffee gardens. Over the region, ' multistrata ' gardens supported the greatest number of species. However, all coffee types had lower taxonomic diversity of birds than did forest. Frugivores, and birds of high conservation dependence, were poorly represented in coffee gardens. Microhabitat use by birds was significantly different between habitats, and it appeared that the birds did make use of structural features as they became available. Farmers indicated that shade trees had benefits such as sheltering coffee plants, and providing produce, but were also apprehensive about over - shading. Many claimed that bird assemblages have changed, yet while describing habitat loss as a past problem, few people felt that forest loss would cause bird deaths. Most farmers believed that coffee gardens had potential to provide useful bird habitat. Interviewees believed that both Government and the community were responsible for conservation. Many showed interest in co - operative conservation programs, particularly if they allowed farmers flexibility, or if they involved incentives related to land tenure. There was also interest in market - based schemes such as eco - certification. The primary action needed for conservation of Sumberjaya ' s birds is to minimise ongoing forest degradation. This may be achieved by linking incentives such as land tenure to forest protection. Capacity to create a certified coffee scheme may be limited by poor coffee quality and inappropriate garden characteristics. Farms maintained primarily for coffee production showed limited value for rainforest - adapted birds. However, the Krui damar gardens suggest a model, which as a forest buffer zone, may allow a more gentle spatial transition from agricultural to forest conditions. / Thesis (Ph.D.)--School of Social Sciences, 2005.