Drivers and trends in the extinction risk of New Zealand's endemic birds

New Zealand is well known as the “land of birds” with 168 extant native breeding species within an area of 270,000 km2. About 40 endemic avian species have gone extinct since human arrival 700 years ago, and a high proportion of the remaining ones are currently threatened with extinction. Here, we compile a retrospective assessment of the extinction risk of New Zealand's endemic birds from the 1980s to the present date using global and national information. We projected trends in extinction risk of species during the last four decades as well as trends for species with different life-history characteristics using the Red List Index (RLI). Overall, the RLI of New Zealand endemic birds has decreased from 0.83 in the 1980s to 0.68 in the 2010s, indicating a higher risk of extinction today than 40 years ago. The conservation status of 23 species (64%) deteriorated throughout the study period. We found that flightless and large species are more likely to have a decline in conservation status compared to volant and small species. Ground-nesting birds and those with long incubation times also face higher extinction risk compared to species nesting above 1 m height and short incubation periods. Species classified as habitat specialists and inhabiting water systems showed a more rapid increase in extinction risk than non-specialist species or those inhabiting forests. Our retrospective assessment can help conservationists to identify the characteristics that make endemic birds more likely to face a higher risk of extinction. Integrating historical conservation assessments and species' traits with extinction risk will improve our ability to manage and protect endangered species.