Energy Requirements of Australasian Gannets Morus serrator (Gray) at a Breeding Colony

Abstract

A model and empirical data (based on regurgitation weights from adult gannets and chicks) are used to estimate the energy requirements of the Australasian Gannet during the 1980-81 breeding season at Motukaramarama gannetry in the Hauraki Gulf, New Zealand. The model calculates the daily energy requirements of males, females, non-breeders and chicks using information from a study over three seasons (1978-80) at this gannetry. Output precision of the model is largely determined by a few parameters: the Kendeigh equation for daily existence energy requirements and the proportion of foraging time spent in flapping and gliding flight. The model suggests that two feeds are required per foraging trip to cover the costs of metabolism and rearing a chick. It is estimated that gannets take about 7% of fish production in the Hauraki Gulf within the 61 km² feeding range from Motukaramarama gannetry. This represents approximately a quarter to a third of total predation by seabirds on fish production.