Vegetation composition and phenology of Mokoia Island, and implications for the reintroduced hihi population

Hihi (or stitchbird, Notiomystis cincta) is a rare honeyeater endemic to the North Island of New Zealand. Hihi were translocated from Little Barrier Island to Mokoia Island, Lake Rotorua, in 1994. Mokoia is a small (135 ha) island with secondary vegetation, so there was some doubt as to whether the island had sufficient diversity of fruit and nectar sources to support a hihi population. This paper reports data collected in the year after the translocation on the density, distribution and phenology of plants likely to be used by hihi. We address the following questions. (1) How many hihi food plant species are on Mokoia? (2) How are the food plant species distributed over the island? (3) Are there periods when flower and fruit sources are scarce and/or spatially confined? (4) How might the availability of fruit and nectar change with succession or additional planting? There was always a minimum of 2-3 species providing nectar or fruit used by hihi. Most (16/21) of the species providing nectar flowered during the hihi breeding period, from October-February, and most (9/16) of these were canopy tree species. The greatest diversity of fruit sources was from March-May. August-September stood out as the period with the lowest diversity of fruit and flower sources, followed by June-July. While there was no time of year when hihi clearly suffered from shortage of fruit and nectar, we suggest that they may be susceptible to shortages in future years at times when diversity of food sources is low. We recommend further planting that could make the island more suitable for hihi in the long term.