This study relates the species composition, numbers, and habits of a hole-nesting avifauna to its environment in successional stages of a coniferous forest in southwestern British Columbia. Emphasis is placed upon explaining an observed presence or absence of nest-site competition. In two breeding seasons, the hole-nesting avifauna was found to be low in numbers of both species and individuals. Most of these birds were able to excavate their own nesting cavities, and commonly did so, for which activity the habitat generally provided ample opportunity. As the species present often differed widely from one another in the type and placement of their preferred nest cavities, there was usually a surplus of different cavity types present. Secondary hole-nesters either concentrated their activities around the buildings in the nearby town, neglecting the more "natural" sites available; were not obligated to use cavities when nesting; or occurred in such low densities, and were so positioned in the available suitable habitat, as to suggest that nest-site competition had no effect upon the populations. Only scattered indications of nest-site competition were observed in wooded areas. Four species nested in crevices in buildings and in bird boxes in a small town, where their breeding population densities were much higher than in the surrounding countryside. Nest-sites were judged to be present in excess, and nest-site competition, observed infrequently, was so rare, and apparently without significant harmful effects, that it was judged to be of negligible importance as a population-regulating factor. The overall absence of nest-site competition is contributed to not only by the preferences of the species regarding their nest-sites, but also by the fact that the results of their habitat selection processes, and their living habits within these habitats, tend to keep them ecologically distinct. / Science, Faculty of / Zoology, Department of / Graduate

Forest birds located by their calls were related to mapping units of different land resource maps using a new method. The method involved computer programs which use mathematical descriptions of landform, forest canopy heights, and the nature of the bird's call to predict the area censused for each bird species from each listening station. Computer programs were also used to display locations made from each station, and to associate the locations and areas censused with different mapping units. Yellow-bellied Sapsucker (Sphyrapicus varius), Chestnut-backed Chickadee (Parus rufeseens), Steller's Jay (Cyanocitta stelleri), Winter Wren (Troglodytes troglodytes), Varied Thrush (Ixoreus naevius), and Swainson's Thrush (hylocichla ustulata) were each related to both serai stages and vegetation taxonomic units; while Hairy Woodpecker (Dendrpcopus villosus), Common Flicker (Colaptes cafer), Red-breasted Nuthatch (Sitta canadensis), and Olive-sided Flycatcher (Nuttallornis borealis) were each related only to seral stages. Most species showed a consistent pattern of selection for mapping types with repeated census. Results for the Steller's Jay indicated some change in the use of seral stages between census periods. However, there was no clear trend in use over time, and the observed changes may include effects of flocking which would violate the statistical assumption that locations were independent. Each species had a unique pattern of selection of seral stages and of vegetation types. Species with similar patterns of selection were grouped to form five groups for seral stages and three groups for vegetation types (groups not mutually exclusive). Only Chestnut-backed Chickadee with Yellow-bellied Sapsucker, Swainson's Thrush with Winter Wren, and Varied Thrush with Winter Wren were grouped together both for seral stages and for vegetation types. A more definite preference among seral stages than vegetation types was detected for most of the species studied. However, the Steller's Jay preferred only two of the vegetation types, while it used all seral stages somewhat equally. Most of the species studied preferred older seral stages. Common Flicker, Steller's Jay, and Olive-sided Flycatcher also used younger stages; while Swainson's Thrush selected for stages of medium age. Of the species related to vegetation types, only Chestnut-backed Chickadee did not show some preference for taxonomic units associated with high soil moisture. The preference was most pronounced for Steller's Jay, which concentrated its use on the two wettest types. The preference by Yellow-bellied Sapsucker may be explained by the older trees and snags that survived logging and fire in wet areas. All of the species also used many of the drier types. The data support the hypothesis that land resource maps can be used to predict the occurrence of wildlife. The results suggest that habitat for a wildlife species can be predicted over vast areas if the areas have been mapped, and if significant differences in the habitat value of different mapping units have been documented. The results indicate that the prediction can be improved by combining the predictions from two or more maps. The predicted area and spatial distribution of high-quality habitat can be compared with management policy objectives for the wildlife species. The predicted change in available habitat with planned forest management activities can provide criteria for habitat management. The same land resource maps may be used for many wildlife species, thereby facilitating multi-species habitat management. / Forestry, Faculty of / Graduate

In 1960-63 populations of the song sparrow (Melospiza melodia (Wilson)) were studied on some of the islands along the Pacific Coast of southern British Columbia. The general problem was to find the factors that might be responsible for the regulation of numbers of any small passerine species. A more specific problem was to explain the extremely high population density of the song sparrows on Mandarte Island compared with densities elsewhere. Most individuals on Mandarte Island were colour marked, and changes in population density and behaviour were observed throughout the breeding season and at intervals during the rest of the year. Environmental conditions on Mandarte Island were compared with those on other islands in the area. All islands were alike in having similar weather and few predators; they differed in the kind of vegetation. The high density of the Mandarte Island population seems to have been a result of the simplicity of the habitat, which favours song sparrows and not their potential competitors, and of the adaptability of song sparrows in utilizing common feeding grounds in undefended areas outside their usual habitat. The critical period in the regulation of numbers was the autumnal territorialism, when increased territorial activities resulted in heavy losses and emigration of the young to areas with lower densities. / Science, Faculty of / Zoology, Department of / Graduate

The objectives of the study were to determine the year-round distribution and habitat selection of four marsh passerine species, as described by vegetation type and its physical characteristics, and to investigate interspecific competition as a factor in the habitat selection of the Long-billed Marsh Wren and the Red-winged Blackbird. Fulfillment of these objectives should help the B.C. Fish and Wildlife Branch to assess the effects of their management plans on marsh passerines. I determined the abundance of four passerine species in different vegetation types via marsh census transects over the period of one year. Nesting habitat and breeding information on marsh wrens and redwings was obtained via nest study plots. The results were: Areas traversed from the central and deepest marsh outward towards higher ground are inhabited by redwings, marsh wrens. Common Yellowthroats, and Song Sparrows, respectively. Habitats of wrens and redwings are spatially and temporally segregated. Wrens use the "Dense Spiraea" (Hardhack shrub) habitat extensively, while redwings use it hardly at all in the marsh. Similarly, redwings are abundant in Scirpus cyperinus (Hairy-seeded Bulrush), whereas wrens seldom use this habitat. Both wrens and redwings use other vegetation types, but redwings use them in the late spring, whereas wrens use them in the summer. Both wrens and redwings have lower reproductive success when nesting in close proximity than when nesting apart. This supports the hypothesis that interspecific competition exists and indicates that selection may favour habitat segregation. I also found mutual suppression of reproductive success when the effects of different vegetation types were removed. The results were not statistically significant however, possibly due to small sample sizes. Of the observed differences between the physical nest site parameters of wrens and redwings, vegetation height and presence and/or depth of water require further investigation as factors in the habitat selection of the two species. Bren-wren competition does not appear to affect wren nesting success in the present study marsh. Management recommendations are given based on the objective of maintaining and possibly enhancing bird species diversity in the study marsh. / Science, Faculty of / Zoology, Department of / Graduate