| Summary: | Black-fronted terns/Tarapirohe (Chlidonias albostriatus) are endemic to New Zealand, where they are currently listed as a nationally endangered species due to their small and declining population. They breed almost exclusively in braided rivers in the east of the South Island, where they are vulnerable to several threats, particularly introduced mammalian predators. Current conservation is focused almost exclusively on controlling mammalian predators around black-fronted tern colonies. Conservation actions away from breeding colonies are hindered by large knowledge gaps around habitat preferences while foraging, foraging range, and migration routes away from colony sites and significant wintering areas. This study used GPS trackers to follow the movements of black-fronted terns, the first time this technology has been applied to this species. In November and December 2020, 34 black-fronted terns were caught and fitted with GPS devices in colonies in the Cass and Ohau rivers of the Mackenzie Basin. During the 2020/2021 breeding season, these terns primarily foraged in high-producing exotic grassland (irrigated paddocks) and avoided areas of low producing and depleted grassland. While foraging, the terns spent 87.6% of their time within 10 km of the breeding colonies and >99% of their time within 25 km of their breeding colonies. One individual black-fronted tern was tracked to 92.2 km from its breeding colony, visiting three major river systems in 24 hours. The mean GPS point distance from the breeding colony was significantly higher for terns from the Ohau compared to terns from the Cass, likely due to favoured foraging areas of high producing exotic grassland being further from the Ohau colony than this habitat is from the Cass colony. Terns from both colonies were found to have nocturnal roosting areas at river deltas near their respective colonies, the first evidence of breeding black-fronted terns roosting away from their breeding areas at night. Following the breeding season, the terns left the Mackenzie ...
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