The size and distribution of colonies of burrow-nesting petrels is thought to be limited partly by the availability of suitable breeding habitat and partly by predation. Historically, the availability of safe nesting habitat was restricted in New Zealand, due to the introduction of rats by humans. More recently, however, habitat has been restored by rat eradication. Petrel colony growth is mediated by both positive and negative density dependence, although it is unclear if, or how, density dependence will affect patterns in post-eradication colony recovery.
In a Festuca novae-zelandiae short tussock grassland in South Island, New Zealand, we tested the propositions (1) that present regional trends in vascular plant species-richness in tussock grasslands are independent of current pastoral management, and (2) that grazing retards the invasion and dominance of nonnative species, particularly where soil resources are not limiting. Sheep and rabbit-grazed, ungrazed, ungrazed+fertilised and ungrazed+irrigated treatments were applied in a replicated experiment that was sampled annually from 1988 to 2000.
Two conservation tools have been developed over the last 10–15 years for species on the New Zealand mainland that are vulnerable to introduced mammalian predators: landscape-scale predator trapping networks, and eradication of predators within mammal-proof exclosures. We tested whether these tools would allow population growth of critically endangered grand skinks (Oligosoma grande) and Otago skinks (O. otagense) over three years.