Probability of survival and breeding for juvenile canvasbacks / Micheal G. Anderson, Mark S. Lindberg, and Robert B. Emery.

Includes bibliographical references (pages 395-397).

Few studies have examined factors affecting the probability of recruitment into breeding populations by
juvenile ducks. We were able to do this for juvenile female canvasbacks (Aythya valisineria) at Minnedosa, Manitoba,
Canada, 1983-1988 by combining estimates of duckling survival, annual survival, and breeding probability. Annual survival
probability increased with duckling weight, declined with advancing hatch date, and was lower in years with more
liberal than conservative harvest regulations. Breeding probability was lower during years with relatively dry wetland
conditions than years with wetter conditions, and it also declined with advancing hatch date. Estimates of breeding
probability ranged from 0.54 to 0.94 forjuveniles and 0.74 to 0.95 for adults. Recruitment probability forjuveniles ranged
from 0.12 to 0.28 at the mean of the covariates (body mass and hatch date) and from <0.01 to 0.43 at the extremes. More
than 54% of the recruits were ducklings produced in nests that hatched early. The per-capita contribution of recruits
by hens that hatch nests early may be even more disproportionate because clutch size and nest success generally decline
with advanced laying date. Managers should recognize that late, dry breeding seasons will likely result in poor recruitment
of hatched ducklings. Where possible, habitat management should facilitate early nesting by canvasbacks.