Survival and sex ratio in a mainland population of bellbirds (Anthornis melanura)
|Title||Survival and sex ratio in a mainland population of bellbirds (Anthornis melanura)|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors||Sagar, PM, Scofield, RP|
|Type of Article||Full Article|
|Keywords||banding 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.