Comparison of Time-Budgets for Mainland and Outer Chetwode Island Populations of Adult Male South Island Robins
- Zoology Department, University of Canterbury, Christchurch, New Zealand
- Present address: Wildlife Service, Department of Internal Affairs, Private Bag, Wellington, New Zealand
Mainland robins forage less and spend less time in interspecific interactions than do Outer Chetwode Island birds, but devote more time than the latter to vocalising, body maintenance and partner-interactions. Outer Chetwode Island males forage for a similar proportion of time throughout the day, but mainland birds forage less, and spend more time on vocalising and partner-interactions, in early and mid-morning than at other times.
From the comparison it seems that the first priority of a robin is to find enough food to meet maintenance needs. When more time has to be spent finding food, that devoted to several other activities declines. Once sufficient food for metabolism is found, "spare" time is devoted to body-maintenance. The activities of least importance to robins in April, May and June are those related to reproduction, such as vocalising and partner-interactions. The birds' diurnal patterns of activities are such that most reproductive behaviour occurs in the early morning, a time of day when foraging efficiency is probably low, so that these activities take place when they have least effect on time required for foraging.