Pacific
26 Jan 2016

New Zealand Fairy Tern – critically endangered tiny tern faces new threat

Mangawhai Harbour and New Zealand Fairy Tern. Photos by Karen Bair and Brian Chudleigh
By Karen Baird

Around half of the ten or so New Zealand Fairy Tern pairs remaining in the world breed at the beautiful Northland harbour of Mangawhai. They nest on the enormous sandspit where the Department of Conservation and NZ Fairy Tern Trust maintain a trapping programme for predators and the nests are closely monitored during the breeding season.  However in recent years the so-called Mangawhai Harbour Restoration Society (MHRS) have decided they want a mangrove-free harbour and applied to the planning authorities to allow removal of mangroves. In 2012 the Environment Court allowed for some removal in the middle harbour which was carried out this past winter. Conservationists have been concerned that removal of mangroves would deplete one of their major food resources, the gobies which live and feed amongst the mangrove pneumatophores. A foraging study was carried out by Karen Baird from the New Zealand BirdLife partner, Forest & Bird in collaboration with other scientists and published in Bird Conservation International (Ismar et al, 2014: Foraging Ecology and Choice of Feeding Habitat of the New Zealand Fairy Tern Sternula nereis davisae). The study showed that NZ Fairy Terns feed their chicks on these mangrove inhabiting gobies, preying on them when they move out of the mangroves at lower tide levels and into channels and pools on the tidal flats.  

MHRS have now unveiled plans for a ‘stage two’, to remove more mangroves. This is despite a ruling already by the Environment Court that the area they’ve targeted should remain. There is increasing pressure in northern New Zealand from Tauranga northwards for councils to relax planning rules around mangroves which have previously enjoyed reasonable protection due to their high ecological values.  

Mangroves are continually the target of prejudice, considerable misunderstanding and what amounts to a concerted campaign often based on misinformation.  These negative views on mangroves include that they are: an introduced ‘pest’ plant which is taking over our northern harbours, limiting people from enjoying open space for speed boats and jet skis;  obstacles to marina developments and reclamations, and are seen by developers as reducing the attractiveness of the coastal properties they hope to sell.

Mangroves are native to New Zealand. Their ecological value as nurseries for marine life is well known, they are home to threatened bird species such as the Australasian Bittern and Banded Rail, and act as natural buffers protecting shorelines from erosion.

For the NZ Fairy Tern more mangrove removal could spell disaster, if it is not already too late given the extent of the clearance work to date. It is critical that these terns can access productive foraging grounds near to their breeding sites, especially along the mangrove lined channels of the Mangawhai Harbour. This allows sufficiently frequent nuptial feeding of the nesting female when she’s incubating, chick feeding and post-fledgling tuition which runs for an extended period in this species. There are warning signs from across the Tasman. The reproductive failure in the closely related Australian Fairy Tern at Coorong was the result of lack of suitable prey near their foraging grounds. Baird and colleagues are now conducting a follow-up study of the goby population in the harbour since removal of mangroves so far. In addition Forest & Bird is engaging with the Northland Regional Council who are reviewing their planning documents to encourage recognition of this site (as well as others) as an Important Bird Area requiring greater protection, not less.