New Zealand endemic open-habitat specialist, the Black-fronted Tern (Chlidonias albostriatus), experienced population expansion during Pleistocene glaciation and recent decline

Understanding how climatic and environmental changes, as well as human activities, induce changes in the distribution and population size of avian species refines our ability to predict future impacts on threatened species. Using multilocus genetic data, we show that the population of a threatened New Zealand endemic open-habitat specialist, the Black-fronted Tern Chlidonias albostriatus - in contrast to forest specialists - expanded during the last glacial period. The population has decreased subsequently despite the availability of extensive open habitat after human arrival to New Zealand. We conclude that population changes for open habitat specialists such as Black-fronted Terns in pre-human New Zealand were habitat-dependent, similar to Northern Hemisphere cold-adapted species, whereas post-human settlement populations were constrained by predators independent of habitat availability, similar to other island endemic species.

Automated summary

Understanding the impact of climatic and environmental changes, as well as human activities, on the distribution and population size of avian species is important for predicting the future of threatened species. In this study, we used genetic data to investigate the population changes of the Black-fronted Tern in New Zealand. We found that the population expanded during the last glacial period but subsequently decreased after human arrival, indicating that population changes were habitat-dependent and predator-constrained.