Black stilt are now rarest of birds

Press, 23 April 1980, Page 21

Black stilt are now rarest of birds

By

OLIVER RIDDELL

New Zealand has become accustomed to hearing of native bird species on unknown and remote offshore islands, or in the depths of the North Island bush, being on the verge of extinction. But the country’s rarest mainland bird is n.ot the well-publicised kokako or kakapo; it is the black stilt of the McKenzie Basin.

The black stilt vyas relatively common in the South Island and southern North Island 100 years ago, nesting as far north as Rotorua. But a rapid decline occurred and 50 years ago they were limited to inland Otago and Canterbury.

This decline has continued steadily. According to the Wildlife Service, there has been a 25 to 30 per cent decline in numbers since 1973. The winter 1979 count gave an adult population of .only 50 to 55 birds

comprising only 20 breeding pairs plus a surplus of males.

Studies by Dr Ray Pierce, of the zoology department of the University of Otago, have shown that in spite of the massive disruption of the breeding grounds of the black stilt in the McKenzie Basin as a result of hydro-electric development, a more suitable habitat is available there than there are black stilts to fill it.

Predation is by far the most important cause of the decline in numbers. There are five potential predators of the black stilt in the region — ferrets, feral cats, Norway rats, hedgehogs, and harriers. Moves are being made to combat these predators and to protect the remnants of the species. In case these prove unsuccessful, the Wildlife Service has begun a pr.o-

gramme to breed black stilts in captivity, at its breeding station at Mount Bruce in the northern Wairarapa. Ten birds have been hatched in captivity. Although successful rerelease into the wild is a long way off, at least the species should be saved by this method — as have the takahe and saddleback. The programme to protect the black stilt in the wild is being led by Dr Pierce. A hectare .of prime black stilt breeding ground at Mailbox Inlet on Lake Tekapo will be protected by wire-mesh fence, with an outward overhang and an electric wire on top. Power will be from solar cells developed at the University .of Canterbury, with a battery back-up. This fence is designed to

keep ferrets and feral cats, in particular, out of an area in which black stilts are known to breed. Dr Pierce, helped by the Canterbury and South Canterbury branches of the Royal Forest and Bird Protection Society, hopes to have the fence up before the 1980 breeding season begins in August. The society is providing 56900 for fencing and maintenance. The money will be handed over to Dr Pierce by the society’s national conservation officer (Mr David Collingwood) this week-end. Black stilts range over most of the country, but now breed in very restricted areas, and the society felt that as a national body -with 31,200 members it ought to be involved.