No description available.

Feeding ecology of breeding House sparrows was studied in a rural settlement in the Czech Republic. Area of home range and feeding habitat selection in relation to farming practices and vegetation management in the study area was examined.

I consider the relationship between natal dispersal, the acquisition of breeding resources and the proximate maintenance of the mating system in a population of song sparrows (Melospiza melodia) resident on Mandarte Island, B.C.. The general hypothesis tested was that intrasexual competition for the resources that limit reproduction in each sex is the main factor affecting patterns of natal dispersal, territory turnover and mating system organization. This study reveals differences in the competitive ability of individuals and the consequences of these for natal dispersal, territory acquisition and the ability to monopolize mates. In this population, natal dispersal, territoriality and the mating system are related through the common mechanism of intrasexual competition for breeding resources. This competition affected reproduction within each sex, and in the opposite sex, raising potential conflicts of interest between mated males and females. I identify correlates of competitive ability, and consider how individuals of each sex maximize the number of young they raised. All suitable habitat was defended even at low density, resulting in high levels of competition for space. Song sparrows contested for territories year-round. Most settlers were yearlings, but several males were older and had previously owned a territory. Most floaters settled by evicting owners from all or part of their territories, in contrast to the assumption of most models of dispersal that floaters gain territories only after an owner's death. Relative age and dominance within cohorts affected recruitment and territorial status in the year following hatch in each sex. Differences in age also affected territorial and mating behaviour, particularly in males. Although competitive ability varied with age, differences in competitive ability between males persisted through life. Approximately 9% of male breeding attempts occurred after a male territory owner had evicted a neighbour and thereby gained access to an additional female. Polygynous males raised more young than monogamous males. Females vigorously defended their territories against female intruders, presumably to prevent polygyny by their mates. Females in polygynous groups often lost the aid of their mate, and raised fewer young, because polygynous males did not aid two females simultaneously. Adding supplemental food altered female time budgets, increased their ability to prevent settlement by female floaters, and increased their reproductive success. This suggests that females are constrained in the amount of time they can spend in territory defence by time spent foraging. The maintenance of monogamy was affected by differences in the abilities of individual males and females to defend their territories against intruders of the same sex. Dispersal distances were similar among sexes, in contrast to the usual pattern of female-biased dispersal in birds. Given the intense territorial behaviour of males and females, this study supports the hypothesis that biases in dispersal arise when territory establishment is substantially more difficult in one sex than the other. Dispersal on Mandarte was unrelated to inbreeding, common parentage, or reproductive success. However, emigrants from Mandarte were socially subordinate birds that must have outbred if they settled successfully. Female emigrants from local populations in the vicinity of Mandarte may settle more often than males. Dispersal occurred as young birds established ranges in the period following independence, from which they challenged or replaced owners. Adding food during the breeding period reduced dispersal in males and females in late summer and the following spring. Competitive ability probably affects dispersal from the natal population, the likelihood of settlement, and the time of settlement for those birds that remain in the natal population. / Science, Faculty of / Zoology, Department of / Graduate

Aging is an underlying risk factor for many major diseases including cancer, cardiovascular disease, and neurodegeneration. Yet we still do not know the full extent of how our bodies age and what determines our lifespan. One mechanism that may play an important role are telomeres, which are protective caps at the end of chromosomes. Telomeres are directly linked to longevity and can be lengthened by the enzyme telomerase. Early life telomere length is critical for lifespan, but we do not know how telomerase performs during this period. Whether variation in telomerase levels can influence telomere length and loss during development with consequences to longevity is still unknown. This thesis focuses on the role of telomerase during post-natal development and its response to stressors and activators with effects on telomeres. Taken together this research enhances our understanding of how telomerase acts and influences telomere during post-natal development.

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For most taxa, maximizing fitness depends on maintaining access to adequate resources. Territories provide exclusive use of resources for an individual or a family group, thus facilitating successful reproduction. The economic defensibility of a territory depends on the quality, abundance, and distribution of its resources as well as the amount of competition that an individual must endure to maintain exclusive access. The benefits of defense must outweigh the costs for territoriality to be profitable. Territory owners may benefit from territories with high quality resources, but they also may incur greater costs defending these resources from competitors. In contrast, territories with poor quality resources provide fewer benefits to an owner but also may have fewer competitors vying for those resources. Resource quality may change over time, especially in habitats in which periodic ecological disturbances, such as fire, occur. As a result, the cost-benefit equation of defensibility also changes over time. The Florida Grasshopper Sparrow (Ammodramus savannarum floridanus), an Endangered subspecies, is a habitat specialist endemic to the Florida dry prairie, a pyrogenic ecosystem found only in south-central Florida. As a result A. s. floridanus has evolved with frequent fires and its demography is strongly influenced by the structural habitat characteristics, such as sparse woody vegetation and large amounts of bare ground that occur with frequent fire. The objective of my study was to determine what factors associated with fire (i.e. habitat structure and prey abundance) affected the "decisions" of male A. s. floridanus to defend a territory. I hypothesized that fire and the resources resulting from fire would have an impact on territory size and placement. I predicted that territories in more recently burned habitat would be of higher quality and that sparrows would avoid areas with a longer time since fire. I conducted my study at Kissimmee Prairie Preserve State Park in Okeechobee County, FL. One half of my 100-ha study plot had experienced two growing seasons since the last fire and the remaining half had experienced only a single growing season since fire at the start of my study. I mapped territories of all males within my study plot twice over the breeding season; once during the early season (nest building and incubation) and once during the late season (nestling and fledgling stages). In addition, during each survey I collected arthropods and surveyed vegetation composition within territories and at random, unoccupied points within the study plot. I compared the differences between the habitat characteristics of territories and unoccupied areas, the differences between the territories of the males that occupied the two-year rough and those in the one-year rough, males that abandoned their territories mid-season and those that remained in the study plot, and the seasonal changes in territory characteristics between the early and late season territories of males that persisted. My results indicate that A. s. floridanus selects certain habitat characteristics in which to place territories. Males preferred areas with fewer shrubs and more bare ground, which is consistent with previous studies. Prey biomass did not differ between territories and unoccupied areas. Nonetheless, although the mean mass of individual arthropods was larger in unoccupied areas, the numerical abundance of orthopterans, damselflies, and spiders was significantly higher in territories than in unoccupied areas. Sparrows were more likely to abandon their territories if they occurred in the two-year rough as opposed to the one-year rough. Territories in the two-year rough were significantly larger, had poorer quality habitat, and tended to have less prey than those in the one-year rough. The sparrows that persisted throughout the season significantly increased their territory size in the late season; however, very little spatial shift occurred, suggesting that they merely increased their territory size rather than moved to new sites. Early-season territories in the one-year rough were completely exclusive, but late season territories showed considerable overlap, suggesting lack of defense and a shift toward home ranges as opposed to exclusive territories. The habitat quality in late-season territories decreased (more shrubs, less bare ground) from the early season. Unexpectedly, however, the biomass of prey increased. This increase coincides with an increased demand for prey because sparrows are provisioning young. It seems likely that the costs of defense increase at this time because time and energy spent in defense come at the expense of time spent provisioning young. Because prey increases in the late season, the need to defend exclusive territories may decline.

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No description available.

Birds are one of the best studied animal groups in the world but are also amongst the most endangered. The wealth of ecological information has shown habitat protection to be vital to bird biodiversity, but habitat loss and degradation continue to defeat conservationists. / Community-based biodiversity conservation efforts have been recently recognized as an important option for safeguarding ecosystems while reducing land use conflicts arising from the material, cultural and spiritual needs of local inhabitants. Community involvement is particularly critical for conservation in anthropogenic habitats. Few studies have linked the ecological impacts of community land use practices with the auto-ecological requirements of dependent bird species. In this study I examine the conservation possibilities for the endangered Sierra Madre sparrow (Xenospiza baileyi) by considering three basic elements: the ecological requirements of the bird, the effects of traditional land use practices in shaping the habitat, and the economic and social conditions that influence current and future land use decisions. I draw on ecological field studies, on traditional ecological knowledge systems, and studies of the political ecological context that influences local practices. / The studies were carried out from 2000-2003 and employed a combination of ethnographic, participative and spatial-ecological approaches to address human-land interactions and their impacts on the sparrow habitat. Social data were obtained through nine workshops which included site visits, transect walks, participatory mapping, oral histories and semi-structured interviews. Ecological data were obtained from landscape ecology analysis, vegetation post-disturbance assessments and detailed bird's nest-site selection analysis. / Results indicate that local people, principally herders, hold a rich knowledge of fire use to achieve diverse purposes, including pasture renewal, grassland maintenance and grass species selection, and prevention of dangerous fires. In order to accomplish their goals, herders have established rotational fire and grazing regimes that consider timing, frequency, location and extent of these disturbance-based practices. This rotational system was found to benefit the Sierra Madre sparrow by maintaining the grassland at the scales needed by the sparrow for nesting. Multiscale habitat recommendations for the species' conservation were derived from this socio-ecological interaction and dynamics. / Unfortunately, external conservation perspectives and interests and internal land tenure conflicts have altered this rotational regime and local perspectives on resource management that threaten the resilience of this social-ecological system. Consequently, traditional ecological knowledge on grassland management can be on risk of disappearing and, with it, important native grasses and grasslands are being made vulnerable. The survival of the Sierra Madre sparrow in particular and of associated biodiversity in general, is in peril if these conflicts are not solved in a relatively short time. A community-based fire co-management program is recommended to promote integrative bird conservation-local development scenarios.

Many grassland songbird species exhibit sensitivity to patch size in North America’s fragmented prairie ecosystems, but the mechanisms explaining this area sensitivity are not well understood. I tested the effects of patch size and artificial conspecific location cues (song playback and decoys) on grassland songbird abundance in 23 northern tall-grass prairies in Manitoba, Canada, in 2010 and 2011. Richness and relative abundances increased with patch area; this effect was not explained by differences in local habitat structure, patch configuration, and adjacent matrix. Artificial cues elicited putative territory prospecting in small, previously unoccupied treatment patches from two focal species, Savannah Sparrow (Passerculus sandwichensis; n=3 treatment sites) and Le Conte’s Sparrow (Ammodramus leconteii; n=4 treatment sites), but not in control patches (n=3 for both focal species). Social information may influence the focal species’ settlement decisions, but the lack of permanent settlement response suggests social cues are unable to reverse their area sensitivity.