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This thesis is the first full-scale historical treatment of Canadian ornithology from 1860 to 1950. Ornithology is one of the most important branches of modern biology, and ornithologists were pioneer researchers in the areas of evolution, systematics, animal behaviour, zoogeography, migration, population biology and ecology. The institutional development of ornithology in Canada was much retarded by the prevailing utilitarian attitude towards science with its lack of funding for fundamental research. It was not until the second decade of the twentieth century that ornithology became part of the scientific establishment of the Canadian government. Despite this, Canadian ornithologists, in face of considerable difficulties stemming from the lack of encouragement and financial support, pursued pioneering studies in migration, behaviour and population biology of birds. Their research contributions were instrumental in taking ornithology from nineteenth century natural history to twentieth century avian biology.

Barred Owls were located through audio playback surveying searching in southern Manitoba. Sixty-one confirmed home ranges were located and nine nest sites were located. Mean diameter at breast height and cavity depth and width were determined to be limiting factors governing Barred Owl distribution. Barred Owl habitat use was examined at two scales: immediately around nest trees and within estimated breeding and non-breeding home ranges. Barred Owl breeding and non-breeding home ranges had significantly more hardwood and mixedwood than random plots. Barred Owl breeding season commenced in early March, egg laying in early April, hatching in early May, and fledging at the start of June. Mean and standard deviation of clutch size were 1.91 ± 0.83. Barred Owl diet was determined to be generalist in nature. Dietary breadth was calculated, using Simpson’s formula for measurement of diversity in a sample, of D = 0.1525.

Barred Owls were located through audio playback surveying searching in southern Manitoba. Sixty-one confirmed home ranges were located and nine nest sites were located. Mean diameter at breast height and cavity depth and width were determined to be limiting factors governing Barred Owl distribution. Barred Owl habitat use was examined at two scales: immediately around nest trees and within estimated breeding and non-breeding home ranges. Barred Owl breeding and non-breeding home ranges had significantly more hardwood and mixedwood than random plots. Barred Owl breeding season commenced in early March, egg laying in early April, hatching in early May, and fledging at the start of June. Mean and standard deviation of clutch size were 1.91 ± 0.83. Barred Owl diet was determined to be generalist in nature. Dietary breadth was calculated, using Simpson’s formula for measurement of diversity in a sample, of D = 0.1525.

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The breeding bird assemblages of blanket bog and moorland habitats in the United Kingdom are of special international importance. They are characterised by species drawn from arctic to temperate regions breeding at high density and showing a particular affinity for open, in parts waterlogged, grazed and burned landscapes. Much recent debate has focussed on the effects of conifer plantations on the distribution and breeding success of these birds. This study concentrates on differences in breeding distribution and success of selected moorland birds. On blanket bog in Caithness and on heather moorland in Grampian Region, moorland waders <i>Charadrii</i> and red grouse <i>Lagopus lagopus scoticus</i> were counted using three methods cross-checked against each other; a) transects using trained dogs, b) listening for calls at dawn and dusk, and c) daylight transects without dogs. Counts were done on afforested ground and adjacent 'edge' areas, and on open moorland far from trees. In Caithness, densities of moorland waders on afforested ground started to decline as soon as planting began, and none was found inside plantations > 7 years old. Red grouse densities on afforested ground in Caithness and in Grampian rose higher than on open moorland areas during the first five years after planting, before declining. It is suggested that red grouse will disappear from afforested ground in Caithness 8-9 years after planting, and in Grampian 11-12 years after. On areas adjoining plantation < 8 years old in Caithness, densities and breeding success of waders and red grouse did not differ significantly from those on open moorland areas far from trees. However, next to older trees the densities of some waders were lower, and breeding success of golden plover <i>Plurialis apricaria</i> and red grouse lower than on open moorland. In Grampian, densities of red grouse did not differ between the different types of area, but breeding success was significantly lower on edge areas than on open moorland. Lower densities and poorer breeding in the two species mentioned above coincided with older nearby trees and taller ground vegetation. However, within areas there were no significant relationships between density and distance from the forest edge for any species, and similarly for breeding success.

Climate change-induced increases in air temperature pose a substantial risk to birds inhabiting arid environments. Terrestrial endotherms, such as birds, can respond to high temperatures by moving to cooler microsites, increasing heat dissipation behaviour and/or suppressing activity. Previous studies have suggested that larger bird species may have a greater suppression of activity (e.g. foraging) than smaller species at high air temperatures. However, this body mass effect may be confounded by drinking behaviour, since different species have diverse drinking ecologies. Using four species of lark that inhabit the Tankwa Karoo National Park, I investigated whether foraging activity and other heat-influenced behaviours were influenced by body mass or drinking behaviour when comparisons were constrained within a single family. These lark species were: Red-capped Lark (24 g), Spikedheeled Lark (25 g), Karoo Lark (29 g) and Large-billed Lark (45 g). There was a two-fold difference in body mass between the lightest (Red-capped Lark) and the heaviest (Large-billed Lark). Moreover, two of these lark species drink surface water (drinking larks; Red-capped and Large-billed Lark) and two do not (non-drinking larks; Spike-heeled and Karoo Lark). I also collected data on other passerines present in the Tankwa Karoo for comparison to the larks. Black bulb thermometers were used to measure the thermal landscape and a combination of instantaneous scan samples and focal observations to record bird behaviour. Black bulb temperatures were as much as 8.16 °C cooler in shaded than in sunny locations. Similarly, black bulb temperatures were as much as 8.02 °C cooler off the ground than on the ground. The results from scan sample data showed limited support that foraging was negatively correlated (although non-significant) with mass between lark species as temperatures increased; however, data from focal observations suggested larks that obtain all water from food had a greater reduction in foraging as temperatures increase than larks that drink free surface water. Within scan samples, heat dissipation and shade-seeking behaviour appeared to be more strongly influenced by whether the species drinks free surface water or not than by differences in body mass. Furthermore, drinking larks dissipate heat at lower temperatures and seek shade at higher temperatures than non-drinking larks. Foraging intensity was higher in the sunny microsites as compared to shaded microsites for all species, suggesting that drinking larks might gain an energetic benefit due to increased heat tolerance. Therefore, non-drinking species may be vulnerable to foraging-thermoregulation trade-offs under climate change. However, ongoing drying trends in the Tankwa Karoo and reduced availability of surface water may make drinking species more vulnerable to climate change in the future than non-drinking species.