Abstract
Lack of knowledge about the behaviour of migratory species during the migratory period is a major barrier to conservation efforts. In this thesis, I focus primarily on differences between the sexes of the bat Lasionycteris noctivagans, during spring migration. Females are pregnant during spring migration and this overlap between migration and reproduction may affect the time and energy management of females as compared to males. In Chapter 2, I examine spring migration phenology of bats at a stopover site. Females arrived earlier than males, likely to give their pups a long growing season. Fat stores appeared to reflect a strategy to provision for upcoming lactation demands. In Chapter 3, I explore stopover behaviour and I show that despite the use of torpor to minimize roosting energy expenditure, cold weather extends stopover duration. There was no sex difference in the length of time spent at stopover. By regressing the time of night bats were captured against their fat and lean mass I demonstrate that bats have greater fat and lean masses closer to dawn, and therefore are likely using stopover periods to refuel. In Chapter 4, I compare sex and seasonal differences in daytime torpor use at stopover. I found that in spring bats used torpor for fewer hours than in autumn, even after accounting for the effect of ambient temperature. Further, females used torpor for fewer hours than males. I propose that these seasonal differences are due to lower prey abundance and predictability in spring; sex differences may be attributable to a higher foraging intensity by females compared to males. Finally, in Chapter 5, I use a radiotelemetry array in southwestern Ontario, Canada to track the spring and autumn long distance migratory movements of L. noctivagans, Lasiurus borealis, and Lasiurus cinereus. No migration corridors were identified in either season. Estimated migration speeds indicate that multiday stopovers are also used in the autumn. These studies combined show that sex affects the spring migration time and energy management of bats. Bat migration research is still in its formative stages and my studies provide new information on bat migration in North America.