Friday, September 18, 2020

Survival and sex ratio in a mainland population of bellbirds (Anthornis melanura)

TitleSurvival and sex ratio in a mainland population of bellbirds (Anthornis melanura)
Publication TypeJournal Article
Year of Publication2014
AuthorsSagar, PM, Scofield, RP
Type of ArticleFull Article
Keywordsbanding recoveries, demography, introduced predators, program MARK 7.1, sex ratio, survival rates

Both apparent annual survival and population composition were estimated, by age and sex, for bellbirds (Anthornis melanura) from a banding study undertaken on a mainland lowland farm at Pleasant Valley, near Geraldine, New Zealand, during the period 1977-97. The model with the fewest parameters showed that apparent survival varied little between sex and years. Although based on only a few recaptures of subadults, apparent survival of adults (0.694 ± 0.042) was slightly greater than that of sub-adults (0.662 ± 0.128). Annual recapture probabilities of adults (0.104 ± 0.024) were also greater than those of sub-adults (0.042 ± 0.029). A comparison of survival and sex ratios between this population of bellbirds and that on the predator-free Poor Knights Islands showed that demographic parameters vary within this species. The mainland population exhibited a lower overall adult survival rate and more even sex ratio than did the island population. Such demographic variation within a species indicate habitat-specific population parameters.

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