No description available.

No description available.

No description available.

No description available.

No description available.

The alms of this study were to quantify various aspects of predator-prey interactions between Great Black Backed Gulls (Larus marinus) and Common Puffins (Frateroula arotica Le) in order to assess the possible long term effects of predation by gulls on a single Puffin colony and to examine the possible influence of avian predators on Puffin social behaviour. Kiore has been little quantification of the extent of Great Black-Backed Gull predation of Puffins throughout the gull breeding season. Chapter One extends data already published on gull predation of Puffins on the island of Dun, St Kilda, by showing what proportion of gall diet comprised Puffins and by indicating the importance of Puffin prey to gull breading success. Chapter Two describes the ranging behaviour and hunting success of gulls on Dun. Gulls only hunted flying Puffins and concentrated their hunting efforts in areas near, but not directly over, their own nests. Any one pair of gulls shared on average about one third of its hunting range with two or three other pairs of Gulls attempted to catch Puffins most often in areas where Puffins, flying in polarised flocks termed 'wheels', habitually turned in to fly over land or out to fly over the sea. With increasing numbers of Puffins in a wheel, gulls made fewer attempts to catch Puffins and took longer to make a successful kill. The grouping behaviour of Puffins is one of the most striking features of the species' social life at the breeding colony. Chapter Three describes and quantifies temporal and spatial aspects of Puffin grouping behaviour at a. variety of colonies. Differences in the diurnal phasing of the formation of different types of Puffin groups and Abstract (cont.) regularities in the spatial distribution of groups in the sea and in the air indicate that individual Puffins regularly synchronised some of their movements in and around the breeding colony with numbers of other Puffins breeding in or using the same part of the colony. The flight behaviour of an individual Puffin in a wheel flock above a sub-colony was influenced by the number of other Puffins in the wheel, b-wind speed and direction, and by the presence of a hunting gull in the vicinity of the wheel. To conclude, the implications of the present study for the management, monitoring and future study of Great Black-Backed Gulls and Puffins are outlined.

No description available.

The purpose of this study is to investigate experimentally some ecological aspects of social behaviour in Song Sparrows, Melospiza melodia, on Reifel Island, British Columbia. Two main questions are asked: A. Does the temporal pattern of settling on territories influence the number of occupied territories, and hence territory size, and the breeding density in a given area? B. Are the juveniles that obtain territories, when the opportunity arises, the dominant individuals in dominance hierarchies established during the pre-breeding season? A necessary pre-requisite for both questions to be answered is that there exists a surplus of birds which are non-territorial and potentially capable of breeding, but which are prevented from taking territories by the resident territory holders. This also is experimentally investigated. Removal experiments were carried but in the fall of 1972 and the spring of 1973. Subsequent replacements and breeding showed that there was a surplus of Song Sparrows on the study area that were physiologically capable of breeding. All but one of the replacement birds were juveniles, and all were probably of local origin. Two types of removal experiments, simultaneous and successive, were carried out in both the spring and fall. On the Simultaneous Removal areas, total replacement took about nine to ten days. Significantly more territories were taken, and the increases in both spring and fall were about 40%. Further, the mean territory size after the removals was significantly smaller than that before. Finally, territory boundaries were completely rearranged following the removals. The replacement on the Successive Removal areas took upto three to four days. There was no significant difference in the number of territories taken, nor in the mean territory size, after the removals. Further, the territorial pattern was retained. Breeding density on all areas, however, remained much the same before and after the experiments. Therefore, there were several unmated males with territories after the removals, and these unmated males proved to have significantly smaller territories than mated ones. Factors which could have accounted for the different results of the simultaneous and the successive removal experiments are discussed, and a proposed explanation is given. Dominance hierarchies were determined in the loose groups of juvenile Song Sparrows that congregated over the winter at certain localities along the hedgerows. Each group tended to be a discrete unit, although some interchange of individuals (both dominant and subordinate) occurred. The hierarchies themselves were stable and essentially linear, with few reversals and the occasional triangle. The removal experiments presented an opportunity for some of the members of the hierarchies to obtain territories. It was found that dominant males in the hierarchies were the successful ones in establishing territories. Further, in the largest hierarchy, out of 12 juvenile males, 4 from the top 5 obtained territories. Factors which could possibly influence the position of the bird in the hierarchy are discussed, and the possible outcomes of the hierarchy are considered. / Science, Faculty of / Zoology, Department of / Graduate

The ecology of urban birds—populations, foraging ecology, and nest-sites—was studied between 1968 and 1970, mostly in Vancouver, British Columbia. Four census plots in Vancouver, each in a different habitat type, were studied year-round. Additional winter studies were made on two plots each in Sacramento, California and Ottawa, Ontario and on two additional Vancouver plots. Breeding bird densities on the Vancouver plots were lower than those in some other urban areas, but comparable to those in most non-urban habitats. Densities decreased with increasing urbanization. In winter, densities were generally higher than in the breeding season, and were much higher than those in non-urban habitats. Winter densities, unlike breeding densities, increased with greater urbanization. The availability of food is probably a major cause of the high winter densities. Sacramento and Ottawa both had lower winter densities than Vancouver. The species diversity of the urban plots was low at all seasons. This results both from a small number of species and a low equitability (i.e., dominance of the population by a very few species). On the Vancouver plots, species diversity was highest in the breeding season, owing to a higher equitability then. The latter probably results from territorial behaviour, which makes it less likely that one or two species will dominate the community. The urban bird populations were dominated—especially on the most urbanized plots—by House Sparrows, Starlings, and Rock Doves. An attempt is made to explain how the biological features of these three species make them especially well suited to the urban environment. Two types of observations—stopwatch observations and spotchecks —were used, in studies of foraging ecology. This phase of the study was confined to the Vancouver plots. An analysis of the stopwatch observations revealed that nearly every species had a distinctive foraging pattern. The only pair of species which had closely similar patterns were the Starling and the Robin. However, these two had quite different foraging methods and utilized different foods. The spotchecks, being discrete, were amenable to statistical testing. Tests were carried out to see whether the use of different microhabitats corresponded to their availability, and to check for differences between species. In both cases, only tests involving the Crested Mynah failed to show significant differences. This lack of significance is believed to be merely the result of a small sample size. Nest-sites were also studied. Interspecific differences in nest height and placement were demonstrated. A conspicuous feature was the almost total absence of nests near the ground. Cat predation and human disturbance are probably responsible for this. In closing, some general features of urban bird ecology are discussed. The importance of studying the foraging ecology of unrelated species, as well as of related ones, is stressed. While two related species with similar foraging ecology usually occupy different habitats, the same, is probably true of unrelated species to a lesser degree. The foraging patterns of urban birds may be expected to overlap more than those of non-urban birds, and nest-site availability may be particularly crucial to birds in cities. / Science, Faculty of / Zoology, Department of / Graduate

The dispersion of a population of blue grouse was analyzed using data from a breeding range on east-central Vancouver Island. During the summers of 1959-1962, the locations, densities, habitat preferences, and behaviour of grouse were studied using several habitats with varying densities of vegetation. A removal experiment was performed in different habitats to test the effect of interaction and selection of habitat on the dispersion of males. All adult males and a few yearling males were territorial, and territories were spaced in a near-uniform pattern. Within a given season, males removed from their territories were seldom replaced by other adults, suggesting that no surplus of non-territorial adults was present. About half of the yearling males were prevented from establishing territory by the presence of adults, and these yearlings were attracted to the vicinity of territorial males. The location of territories by newly-adult males did not depend significantly on the number of territories already present, even though the tendency toward uniform spacing was preserved. Comparison with other studies indicated that territory size and possibly the fraction of yearling males in the population were inversely related to the density of males. Females restricted their movements while on the breeding range but were not territorial. No pair-bonds were observed but females stayed near territorial males prior to nesting. After the hatch, the locations of females and broods bore no relation to each other or to the positions of males. Interaction apparently had no effect on breeding numbers. All birds preferred sparse vegetation to dense. When compared to randomly-chosen points, territories were found more often in areas with sparse vegetation, elevated points, and patches of open ground. Within open habitats, nests were usually located where cover by logs, stumps, and ground-level vegetation was high, and cover by dead plants and litter was low. Broods were associated with moist areas and other areas having heavy cover by vegetation at the ground level. Chicks apparently dispersed widely between their first and second summers. In their third summer, males usually returned within one-half mile of the positions they used as yearlings. Once territories were established, the owners returned to them in succeeding summers. Females one year and older showed a fairly accurate return to their previous locations. The dispersion was described somewhat theoretically by considering the summer population to be grouped into two types of aggregations. The first, found in the earlier half of the summer, was caused by the attraction of yearling males and lone females to territorial males. Later, hens with their broods were the dominant groupings. The spacing, movements, and habitat preferences seemed to be adaptations allowing such populations to rapidly exploit new habitats. / Science, Faculty of / Zoology, Department of / Graduate