LE3 .A278 2020

2020

Mallory, Mark
Robertson, Gregory

Acadia University

Master of Science

Masters

Biology

Biology

American black ducks were once the most abundant and most heavily harvested species of waterfowl in eastern North America but wintering black duck populations have declined and continue to decline in southern and central regions of the black duck’s wintering range. In contrast,recent ob servations suggest numbers of black ducks wintering in Atlantic Canada are increasing. Despite the extensive amount of research on black ducks, little work has focused on better understanding black ducks that overwinter at the northernmost limit of the black duck wintering range. To build upon the knowledge of wintering black ducks in Atlantic Canada, I examined survival and movements of American black ducks and mallards that winter near the northern limit of their range. To assess survival and fidelity of wintering American black ducks and mallards, I used data from 498 black ducks and 550 mallards captured and banded during the wintering period from 2009-2015 at an agricultural site in western Nova Scotia, Canada. I found virtually no support for models with annual variation in survival, fidelity or reporting probabilities. In general, survival was high and comparable to results from other locations and from birds banded before the fall hunting season. Male mallards and black ducks had a higher probably of survival (72.3% and 88.8% for males > 2 years old) compared to female mallards and black ducks (53.8% and 71.9%). Young male black ducks had a higher rate of reporting than adult male black ducks, suggesting a higher vulnerability to harvest that persists after surviving their first hunting season. Female black ducks had the lowest reporting rate of all groups, and both species showed high winter site-fidelity. Migratory chronology and movements of American black ducks were analyzed using data from 11 black ducks tagged with Platform Terminal Transmitter. These telemetry data revealed that wintering black ducks from my study site contained both longer-distance migrants and locally-breeding individuals. Longer distance migrants moved away from the wintering area to inland areas throughout Atlantic Canada to stage before traveling north to breed as far away as the southern shores of Ungava Bay, Quebec, while some birds remained in Nova Scotia year-round. Results presented in this thesis will inform future population modeling, harvest management and habitat capacities assessments of these two species at the northeastern limit. When future work assesses Atlantic Canada’s carrying capacity for wintering black ducks, researchers and conservationists may want to consider the implications of high rates of survival and fidelity in a population of black ducks that contains year- round locals and migrant birds.

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https://scholar.acadiau.ca/islandora/object/theses:3482