Is the breeding behaviour of nesting seabirds influenced by the presence of a predatory reptile—the tuatara?

Increasing our knowledge of the costs and benefits associated with commensal interactions is necessary both for a better understanding of how ecological communities are structured and for determining conservation actions. We investigated the concomitant use of a burrow by a nesting seabird, the fairy prion (Pachyptila turtur), and a medium-sized predatory reptile, the tuatara (Sphenodon punctatus). Arrival time of fairy prions at the burrow each night was found to be delayed by the presence of a tuatara at the burrow. Use of the burrow by tuatara almost halved the time fairy prions spent at the burrow with their chick. The effect of this cohabitation on each species can be expected to change over both space and time, i.e. with changes in population densities and season. Hence it is possible that in newly established colonies of birds with low numbers in the presence of tuatara, tuatara predation may have a deleterious impact.