Acquisition of foraging skills by Heron Island Silvereyes Zosterops later alis chlorocephala

Age-related differences in foraging efficiency and behaviour were investigated in a population of colour-ringed Silvereyes Zosterops lateralis. First-year birds were less efficient foragers than older birds with second-year birds being intermediate. First- and second-year birds had lower success rates than older birds overall, and for most capture techniques and substrates. First-year birds never attempted breeding while about half of the second-year birds and all of the older birds did. Both learning and selection effects may have been involved in causing the age-related differences in foraging behaviour. Foraging skills appear to improve during the first 2 years of life and selection could remove the least efficient foragers from the population in winter when food is short. That second-year birds, some of which had already attempted breeding, were not significantly more efficient foragers than first-year birds suggests that reproduction is not delayed until adult levels of foraging efficiency have been attained.