Abstract
This study (1) investigated functional (capture rate, foraging success) and numerical (density) responses of bar-tailed godwitsLimosa lapponicato an experimental decrease in densities of their prey, and (2) estimated seasonal depletion of the stock of their main prey, the mictyrid crabMictyris longicarpus, in a subtropical estuary. It was predicted that if intake rates of the godwits are in the vicinity of the gradient section of a functional response curve, i.e. are directly determined by prey density, they will respond rapidly to experimental reduction in the density of their prey. Bartailed godwits did respond rapidly, both functionally and numerically, to a decrease in the density ofM. longicarpus, indicating that their intake rate was limited by food availability. The estimated seasonal depletion of the stocks ofMictyrisby the godwits was 88% of the initial standing stock. Despite the virtual disappearance ofMictyrisfrom sediment samples through the course of a non-breeding season, local densities of godwits did not change between October and March, implying that adequate rates of intake could be maintained throughout their residence period.
