An approximately 228 acres large forested area near Hope, B.C., has been investigated in the mahonietosum subassociation of Pseudotsugeto-Gaultherietum mesic association of the Coastal Douglas-fir Zone. Botanical survey and bird census work by the nest (or territory) mapping method were carried out during two summer seasons. Fifteen ecosystem types are described and their bird population, expressed in average densities per area unit as well as by average biomass is tabulated. Physical environmental conditions, especially pertaining to microclimate, were measured at 55 nests of the eight most common passerine species, and nest placing and construction has been considered at 167 nests of the same species. It has been found that the nesting of these species in their habitats is the function of the present vegetation, physical environment and the adaptive range of the species. In certain species the birds apparently chose nest sites with equable microclimate. In others it was found that the insulation of the nest varies according to the needs indicated by the extremes of the microclimate; again in others the nest material chosen provided the best available resistance to mechanical stresses. While other essential environmental requirements were not studied the results point toward an assumption that microclimate strongly influences the site, height, position, and material of the nests, and ultimately, the selection of nesting habitat of the birds studied. / Forestry, Faculty of / Graduate

The lack of suitable nest sites may be a limiting factor for Western Bluebird populations inhabiting the upper Willamette Valley. Nest box trails have been established on the hills surrounding the Portland metropolitan area. Since their placement, approximately 25% of the boxes available have been used by Western Bluebirds as nest cavities. This study was undertaken to identify factors which might determine the selection of a nest box by Western Bluebirds and the subsequent nest success or failure. The breeding biology of Western Bluebirds using the nest box trail located on Parrett Mountain, Oregon in 1979 was investigated. Breeding season, mean clutch size, average incubation and nestling periods, and level of nest success were determined. Nest box dimensions, placement, and surrounding habitat features were quantified. Potentially important nest site characteristics were examined and tested for association with Western Bluebird nest box use and reproductive success. Western Bluebird nest box selection was random with regard to all of the characteristics studied except Solar Index and Nest Box Density. No correlation was seen between nest box characteristics and bluebird nest success.

A surge of recent work elucidating a role for learning and memory in avian nest-building behaviour has challenged the long-standing assumption that nest building develops under genetic control. Whereas that work has been addressed at describing the cognitive mechanisms underpinning nest-building behaviour, almost nothing is known about either the neurobiological processes controlling nest building or the selection pressures responsible for the diversity in avian nest-building behaviour. Here, I sought to identify both the neural substrates involved in nest-building behaviour and some of those selection pressures. First, I used expression of the immediate early gene product Fos, an indirect marker of neuronal activity, to identify brain regions activated during nest-building behaviour in the brains of nest-building and control zebra finches (Taeniogypia guttata). I found that neural circuits involved in motor control, social behaviour, and reward were activated during nest building. Furthermore, I found that subpopulations of neurons that signal using the nonapeptides vasotocin and mesotocin and the neurotransmitter dopamine located within some of these neural circuits were also activated during nest building, suggesting these cell-signalling molecules may be involved in controlling nest-building behaviour. Next, I found that variation in the amount of folding in the cerebellum, a brain structure thought to be involved in manipulative skills, increased with increasing nest structural complexity, suggesting that the cerebellum is also involved in nest building. Finally, using evolutionary statistical models, I found support for the hypothesis that nest-site competition off-ground and increased predation pressure on the ground in Old World babblers (Timaliidae) led to the co-evolution of building domed nests on the ground. Here, then, I provide the first evidence of potential neural substrates controlling and selection pressures contributing to variation in nest-building behaviour.

[Truncated abstract] Ecosystem engineers are organisms that physically modify habitat in a manner that modulate resource flows and species within ecosystems. Ecosystem engineering is distinct from classical interactions (competition, predation, parasitism and mutualism) in that it does not involve direct trophic exchange between organisms. The term ‘ecosystem engineer’ is a recently adopted one, and we are just beginning to investigate the occurrence and impact of engineers in ecosystems. My thesis explores the ecosystem engineering actions of Wedge-tailed Shearwaters, Puffinus pacificus, in a Mediterranean island, heathland ecosystem. I have approached this by (1) describing and quantifying the physical impact of these engineers, and (2) describing and quantifying the effects that these actions have on three major ecosystem components: the soil, the vascular plants, and the vertebrate fauna. Wedge-tailed Shearwaters are procellariid seabirds that excavate nesting burrows on offshore islands. The birds are colonial nesters, and on Rottnest Island, 17 km off the mainland coast of south-western Western Australia, their colonies have expanded considerably in recent decades. The expansion fits the trend observed in other tropicalorigin seabirds that breed in south-western Australia. In the last ten years, two new colonies have appeared (in a total of six) and the number of burrows on the island has almost doubled, to 11 745 ± 1320SE. In the same period the area occupied by the birds has increased by almost half ...