Environment – Tiritiri Matangi helps hihi back to life

Back in May, Hibiscus Matters reported on a successful translocation of hihi/stitchbirds from Tiritiri Matangi to Shakespear Regional Park. This was the third translocation of hihi to the park and it’s looking hopeful that they will establish successfully. But this is only a small part of a much larger effort to secure the future of this amazing and enigmatic species in which Tiritiri is playing a major role.

Hihi once ranged over most of the North Island’s forests, but by the 1880s, with the advent of mammalian predators and the loss of forest cover, they were eventually reduced to a single population on Te Hauturu-o-Toi/Little Barrier Island of about one to three thousand. In attempts to improve their situation, the government’s Hihi Recovery Group sought to establish new populations in protected areas.

In the 1980s, birds were moved from Hauturu to Taranga/Hen Island, Repanga/Cuvier Island and Kapiti Island. Initially, the birds bred well, but on Taranga and Repanga they gradually declined to extinction. Monitoring on Kapiti suggested that an insufficient year-round supply of nectar and other food was limiting population growth.

Next to receive birds were Mokoia Island (in 1994) and Tiritiri Matangi (several translocations from 1995 onwards). Unfortunately, it was predicted that the Mokoia population would die out without continued support, so the birds were removed. On Tiritiri Matangi, birds were supported by the provision of sugar water and nest boxes and by controlling the impacts of mites on nesting birds. Thirty years later the population on Tiritiri is around 230 to 260 and it continues to increase. It has been so successful that Tiritiri is now the major source population for transfers. Over the past 20 years 653 birds have been provided to other sites.

There are now populations at Bushy Park (from 2013, now steady at around 50 to 60 birds), Kapiti (from 1983, now variable at 100 to 150 and perhaps increasing), Maungatautari (from 2009, population uncertain due to limited monitoring), Rotokare (from 2017, now 120 to 215 and increasing), Zealandia (from 2005, rose to 140 to 160 (by 2017) then fell to 50 to 70) and Shakespear.

In some ways this is a wonderful success story with seven extra populations created. But each of these new sites remains dependent on the provision of supplementary food and, in some cases, nest boxes and mite control (as well as being free of mammalian predators). Despite very significant efforts to study and understand the lives of hihi and translocations to eleven sites, we have yet to establish a successful self-sustaining population, even in sites without mammalian predators. We remain unable to define the characteristics of a site where hihi will thrive unaided, so it seems that Tiritiri Matangi will continue to be a key site for hihi for the foreseeable future.

There’s a Dawn Chorus trip on Saturday October 4 for a chance to experience early morning on the island. Details are on the website (tiritirimatangi.org.nz).