Electronic Thesis and Dissertation Repository


Doctor of Philosophy




Drs. Scott Petrie and Beth MacDougall-Shackleton


Spatial and temporal variation in the density and distribution of waste agricultural grain (grain herein) during staging can affect the carrying capacity of habitats that support avian populations. Such variation in food resources can also have proximate effects on behavioural ecology (e.g., influence optimal behaviour). The Eastern Population of Greater Sandhill Cranes (Antigone canadensis tabida; EP herein) likely began to recolonize Ontario and its historic range starting in the early 1900s and now relies on agricultural grain during migration. Accordingly, ecologists possess little knowledge of how EP crane behavioural ecology may be affected by grain. Thus, my study focused on grain effects on the following topics: 1) age-specific foraging scale and numerical response, 2) age-specific foraging efficiency, and 3) roost use. I used field observation and experimentation, GPS tracking, and GIS analysis to investigate these topics at a key staging area on Manitoulin Island, Ontario, Canada. Although adult cranes remain with offspring during autumn staging and juveniles continue to grow and learn, juveniles did not appear to affect family group field use. Relative food density at a scale of 5 km from feeding fields had the strongest effect on field use, approximately aligning with mean foraging flight distance (6.4 ± 0.15 km) calculated from GPS tracking data. Adult cranes did not forage more efficiently than juveniles; if anything, juveniles may have foraged more efficiently than adults. Alternatively, the social contexts of foragers (e.g., small family flocks or larger mixed flocks) may have obscured age differences in foraging efficiency, grain may not have been sufficiently novel to affect behaviour, or juvenile cranes may learn to forage for grain relatively quickly. Both anthropogenic disturbance and grain affected roost use. Distance to primary paved roads had the most important effect on roost use, although grain density within 12 km of roosts also had an effect. However, road type (e.g., paved, gravel) may not be an accurate index of nighttime traffic when cranes typically use roost wetlands. Thus, I conclude that grain affects crane foraging and roosting behaviour during staging, but effects vary in nature between field use, foraging efficiency, and roost use contexts.

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