Foraging ecology and habitat suitability of the critically endangered New Zealand fairy tern or tara iti (Sternula neresis davisae) in Northland, New Zealand : a thesis present in partial fulfilment of the requirements for the degree of Master of Science in Conservation Biology at Massey University, Albany, New Zealand
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2023
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Massey University
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This thesis aimed to improve scientific knowledge of the critically endangered New Zealand Fairy Tern/Tara iti (Sternula nereis davisae) (hereafter; NZFT) foraging ecology, measuring three key elements; (1) Behavioural time budget analysis; (2) Spatial interactions; (3) Dietary analysis through stable isotopes. Current knowledge of NZFT behaviour has been limited to observational and ad-hoc approaches. Coordinated behavioural observations occurred on 13 individuals (21% of population) throughout the 2021/22 breeding season in Mangawhai, New Zealand. A mean foraging trip length of 17 ± 1 min was determined for adult provisioning NZFT, during which they spent 97% of their time performing foraging related behaviours. I observed 17 flight paths and 25 dive locations outside of the estuary in coastal marine environment. Estuarine habitats accounted for less foraging trips than expected, suggesting the importance of other habitats. With the human population of Mangawhai predicted to increase over the next 30 years, I aimed to understand the current spatial use of Mangawhai estuary and surrounding areas by NZFT and people providing a baseline to support future management. Spatial data collection on dive and resting locations, and activities of humans were undertaken using GIS over the 2021/22 breeding season. Kernel density maps were compared through visual analysis and supported territorial foraging theory. Peak human presence occurred during the fledging period of NZFT chicks, highlighting need for management of human activities within Mangawhai estuary. This study used stable isotopes δ¹³C and δ¹⁵N to provide analysis into NZFT diets using chick feathers. Thirty-one feathers were obtained from four breeding seasons and analysis undertaken following previous methods (Ismar et al., 2014). Reference fish samples (n = 52) were obtained from Mangawhai estuary and Bream Bay, New Zealand. I found a higher proportion of marine prey in 2022 than other years, however, this was not statistically significant. Marine foraging was not shown to influence chick survival. Findings from my thesis highlight the role of the marine environment as an integral part of NZFT foraging habitat during breeding, complementary to estuarine foraging territories. Furthermore, my thesis results provide key baseline data for this species, emphasizing potential impact of increased human pressure.