SURVIVAL RATES OF AUSTRALASIAN SHOVELER DUCKS IN NEW ZEALAND

摘要

We studied survival and movement of Australasian shoveler (Anas rhynchotis) using 883 band recoveries reported by hunters from 4,080 adult and 881 pre-fledged juveniles banded in 2 regions of New Zealand between 1972 and 1985. We fitted several band-recovery models including ones in which the logit of the survival probability was modelled as a linear function of age, sex, banding location, and time. We also fitted models in which the time-effect was expressed as a function of the El Nino-Southern Oscillation index (SOI). In a year in which the SOI was zero (neither El Niño nor La Niña conditions) the survival probability for adult males banded in Otago was an estimated 0.610 (SE = 0.058). The odds of survival for male and female juvenile shoveler were an estimated 0.605 (SE = 0.125) times that for adults; the odds of survival for juvenile and adult females were an estimated 0.631 (SE = 0.129) times the odds of survival for males; and the odds of survival for all birds banded in Southland were an estimated 1.550 (SE = 0.305) times the odds of survival for birds banded in Otago. For birds banded in Southland and Otago, large negative values of the SOI were associated with higher survival and decreased movement of birds away from the banding site. For birds banded in Waikato, the estimated survival probability for males in a year with SOI = zero was 0.724 (SD = 0.045). Across all years, the odds of survival for females were an estimated 0.720 (SD = 0.11) times that of males. In Waikato, El Niño conditions were associated with lower survival and increased movement of birds away from the banding site. We recommend that northern and southern populations of shoveler be managed as separate populations.