Hatch date influences pre-fledging survival of temperate-nesting Canada geese

Among the numerous demographic parameters that influence population size, unbiased estimates of pre-fledging survival remain difficult to obtain for precocial birds. In this study, we used capture–mark–recapture modeling to estimate pre-fledging survival in a population of temperate-nesting Canada geese Branta canadensis maxima that has undergone an exponential increase over the last two decades. We examined whether pre-fledging survival was affected by relative hatch date, initial brood size, mother age, and weather conditions at hatching. Between 2005 and 2014, 8679 goslings were marked with web-tags at hatching at two adjacent sites. A total of 3922 of these birds were initially recaptured and banded before fledging while 338 were recaptured and banded in subsequent years as after-hatching year birds. Multistate models with joint live and dead encounters were used to estimate pre-fledging survival and evaluate the effects of rearing sites, gosling characteristics, and weather conditions at hatching. Pre-fledging survival of Canada geese varied between 0.45 (95% CI: 0.41–0.50) and 0.75 (0.62–0.84) among years and sites with an overall mean of 0.62 (0.54–0.68). Survival rates were lower for late hatched birds and tended to increase with initial brood size and mother age. Weather conditions at hatching did not affect pre-fledging survival. Significant effect of hatch date on pre-fledging survival has often been described in geese nesting in highly seasonal environments (e.g. the arctic) but our findings of such a relationship in temperate-nesting Canada geese indicate that a selection pressure on the timing of breeding can also occur at more stable temperate latitudes.