A model for the conservation management of a ‘secondary’ prey: sooty shearwater (Puffinus griseus) colonies on mainland New Zealand as a case study Original Research Article

New Zealandʹs native birds constitute the supplementary or ‘secondary’ prey of introduced mammalian predators. Predation on secondary prey is inversely density dependent. Small populations will therefore be at greater risk of extinction than large, which escape due to the buffering effect of their size on predation impact. A matrix model of a mainland sooty shearwater (Puffinus griseus) population predicted a mean growth rate of 1.044 (0.967–1.130) with no predation. Survival of adults attending the colony was the most influential population parameter. With predation effects included, colony growth was sensitive to both management intensity and colony size. Small colonies required the removal of almost all predation risk to survive, although the level of management required for growth decreased with increasing colony size. Management intensity may be relaxed as a colony grows and an ‘escape thresholdʹ colony size is eventually reached at which growth continues without predator management.