Year: 1979
Abstract:
Aerial surveys and ground investigations were conducted in the spring and summer months from 1975 to 1977 on a breeding population of White Pelicans (Pelecanus erythrorhynchos) in the Birch Mountains area of northeastern Alberta. In 1975, an undetermined number of White Pelicans bred at Big Island Lake located approximately 20 km northeast of Namur Lake; however, the sighting of only 12 young during a July aerial survey at that location suggested a small breeding flock. Pelicans did not breed successfully at Namur Lake, a previously occupied nesting location, during the course of this study. In 1976 and 1977, White Pelicans established nesting colonies and bred at a rookery site at Birch Lake, located approximately 10 km south of Namur Lake. Aerial photographs taken at the Birch Lake rookery during the height of the nesting season in late May and early June revealed 140 breeding pairs in 1976 and 70 pairs in 1977. Sixty-eight young were raised to the flying stage in 1976, compared with 55 in 1977, resulting in fledging rates of 0.49 and 0.78 young per nesting attempt in those respective years. Calculated breeding success (number of young raised to the flying stage from estimated total eggs laid) was 22.1 percent in 1976 and 35.7 percent in 1977. In 1976, an estimated eight to 20 nests were lost to rising water levels induced by beaver (Castor canadensis) dams constructed on the outflow channel of Birch Lake. Periodic removal of these dams prevented loss of nests in 1977 to flooding. Mortality during the breeding season included an 11.7 percent loss of eggs and a 19.1 percent loss of young in 1977, the only year for which such data were obtained. White Pelicans bred only on island sites located in permanent water bodies. The birds nested on flat or gently sloping terrain which provided loose substrates for nest mound construction. These substrates varied in composition from loose organic soils to gravel with scattered rock. Density and composition of vegetative cover at nesting locations were also variable, being partly modified by the nesting activity of the birds themselves. Pelicans, which were presumably foraging, were observed on water bodies as far as 69 km from the breeding site. Both adults and young demonstrated varying levels of behavioural responses to disturbances occurring near the rookery. The documentation of these responses and other behaviour is presented in a discussion which considers their implications with respect to the potential effects of development of the Athabasca Oil Sands deposits and the anticipated accelerated recreational use of the Birch Mountains wilderness. Management and reclamation strategies are discussed.
