Behavioural ecology of the endangered New Zealand Fairy Tern (Tara-iti) Sterna nereis davisae : implications for management : a thesis presented in partial fulfillment of the requirements for a degree of Masters of Science in Ecology at Massey University
The roles of the sexes in the New Zealand Fairy Term (Sterna nereis davisae) during reproduction were investigated over the 1997/1999 seasons at Mangawhai and Waipu, Northland, North Island New Zealand. Factors which may affect the behaviour of the birds were investigated including time of season, time of day, weather conditions and the state of the tide. As in other terns, the contributions of the male and the female Fairy Tern to reproduction were relatively equal. Courtship feeding, however, appears to be a male-specific behaviour, and the male feeds the chick more than the female when there is a single chick. The level of care of eggs and chicks at night by the female, and of the fledged young by the male, is unclear, but could alter the overall contribution to breeding by the two sexes. In the first season, wind speed caused less absence from young, while time of day and time of season (week) affected incubation, and parental activities. Egg manipulation for management purposes at Mangawhai altered the birds' behaviour, the female being less attentive during the day and it increased the amount of time birds sat on the nest. The state of the tide affected the feeding of young, with increased feeding three hours after low tide. This may be site-dependent because the Mangawhai Fairy Terns also foraged at high tides. Fairy Terns were highly aggressive towards Harriers, Black-backed Gulls and people, particularly when they had young. Fairy Terns also responded aggressively within 75m, the birds at Waipu responding more often because a number of other birds nested in, and passed over, the area. The Fairy Terns preferred highly elevated nest sites, with low vegetation cover, and a high percentage of shell cover. These features characterise nest sites of a number of terns. DNA analysis suggests that copulation behaviour, but not morphology, is adequate evidence for sexing adult Fairy Terns. The sex ration of nine juveniles was five males: four females. The number of adults caught was too small to calculate an adult sex ratio.
This study has implications for future management of Fairy Terns. Eggs at the same development stage should be placed under foster parents, fences should be placed 180m from the nest or chicks, and sparsely vegetated and shell covered areas should be protected and maintainted. Weather conditions, the time of day, and observed absences should be considered before removing eggs from the field. More blood samples are needed for parental and taxonomic studies.