Age and breeding stage-related variation in the survival and harvest of temperate-breeding Canada Geese in Ontario
The abundance of Canada geese (Branta canadensis) nesting in temperate regions of North America has increased dramatically during the past half century. Numbers have reached nuisance levels in many areas and supplementary hunting seasons, which are timed to occur before and after traditional waterfowl hunting periods, are widely employed to limit population growth. We evaluated how changes in hunting regulations have affected population growth, the seasonal age distribution of harvest, and survival rates of temperate-breeding Canada geese banded in Ontario. We found that although the number of geese harvested in the province has increased, population growth has not abated. Annual survival rates (S̄) of locally nesting adults (i.e., after-hatch-year geese captured in brood flocks) have declined in association with harvest liberalization (pre-liberalization: S̄ = 0.78 ± 0.06 SE; post-liberalization: S̄ = 0.74 ± 0.04 SE) and we estimated negative process correlation between hunter recovery rates and survival rates within this group (ρ = - 0.24), which is indicative of an additive effect of harvest mortality on total mortality. However, peak harvest has advanced into early September, which is a time when large numbers of molt migrant individuals are present in northern portions of the population's range. Molt migrant flocks are comprised primarily of subadults and adult geese that failed to hatch eggs (i.e., non-reproductive individuals), many of which are unaffiliated with the local breeding population. We found that hunter recovery rates of non-reproductive geese were greater and survival rates were less than those of locally nesting adults; however, process correlation between recovery and survival rates was weakly positive (ρ = 0.09), which indicates that harvest mortality is at least partially compensatory within non-reproductive cohorts. We conclude that current harvest levels are insufficient to halt population growth and that the influence of hunting, relative to its potential, is diminished by a disproportionate take of individuals of low reproductive value during the early hunting season.
|Keywords||band recovery, Branta canadensis, Canada goose, harvest, Ontario, population control, survival, temperate-breeding, wildlife management|
|Journal||Journal of Wildlife Management|
Iverson, S.A. (Samuel A.), Reed, E.T. (Eric T.), John Hughes, R., & Forbes, M. (2014). Age and breeding stage-related variation in the survival and harvest of temperate-breeding Canada Geese in Ontario. Journal of Wildlife Management, 78(1), 24–34. doi:10.1002/jwmg.636