Enhancing neighbourhood amenities to attract residents isn't just something urban designers do. Ecologists are employing similar tactics in an effort to increase numbers of our rarest native bird.
The New Zealand fairy tern – tara iti (Sterna nereis davisae) is one of the world’s rarest birds. There are less than 40 birds remaining in the world, and of these only nine or ten are breeding-age females. Compare this to the kākāpō population for which there are about 140 birds! Last year only six tara iti pairs attempted to nest, and from this just two chicks hatched. To make matters worse, one breeding female died.
Not only is the number of birds limited, so too are their breeding grounds and the kind of habitat they like to nest in. There are just four main breeding sites: Waipu sandspit, Mangawhai sandspit and Pakiri stream mouth on the east coast of the North Island, and Papakanui sandspit on the west coast of the North Island (Kaipara Harbour). To add to this, tara iti nests on beaches during summer, where they create a nest by scraping a small hollow in the sand where shell accumulates above the high tide mark. This can make their nest sites (and breeding success) highly vulnerable to adverse weather events during the breeding season; the combination of high tides and onshore winds regularly inundate and destroy nests. The potential for such losses may increase with changes in environmental conditions associated with climate change and sea level rise.
We’re working with Te Arai and Mangawhai Shorebirds Trust, Te Uri o Hau and the Department of Conservation (DOC) on a multi-pronged approach to increase the likelihood of the survival of tara iti. Predation by introduced mammals is the main threat to the survival of tara iti, so predator control is being undertaken at the breeding grounds. But the most exciting aspect of our work is using a novel approach to create and enhance shellbanks to safe-guard and increase the breeding habitat available for tara iti.
The largest shellbank project to date is at Waipu sandspit. This project is part of a wider three-year-plan developed by the Tara iti Recovery Group, funded by the Te Arai and Mangawhai Shorebirds Trust and supported by Boffa Miskell, local hapu, Refining NZ, Skyworks Helicopters and the Department of Conservation. Skyworks Helicopters flew in 130 tonnes of locally sourced shells to construct three new shell patches at Waipu. Future breeding sites to be enhanced include Mangawhai and Pakiri. The intention is to increase the number of shell patches available for nesting habitat, as well as the height, attractiveness and size of existing shell patches.
Whether tara iti will accept these enhanced shell patches remains to be seen — project partners are keeping a close eye on whether any breeding pairs move into the newly-created neighbourhood.
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Photo of shellbank by Linda Guzik, Te Arai and Mangawhai Shorebird Trust
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For further information please contact Dr. Leigh Bull
14 October 2019