Download

During a visit to North Brother Island in Cook Strait from 11 October to 6 November 1990, we estimated by quadrat sampling that the 4 ha island supported 1000 pairs of Fairy Prions, 600 pairs of Common Diving Petrels, and 225 adult tuatara. Most Diving Petrels nested below Coprosma scrub, and a few eggs were laid on the surface under dense shrubs. Many prion burrows were in more open vegetation. Burrows of both species were simple and were not shared with tuatara. Some evidence of tuatara preying on unattended eggs was found, but there was no evidence that the endemic Sphenodon guntheri, which is smaller than S. punctatus, fed on adults of either species. Many Diving Petrels, prions, Fluttering Shearwaters and Red-billed Gulls fed in tide rips close to the island. The position of each species in feeding assemblages was related to their dive depths. Diving Petrels in areas of strong currents submerged for only a few seconds at a time, but in areas of calm water dive durations averaged 29 seconds.