Shore plover back on mainland

Forest and Bird, Issue 266, 1 November 1992, Page 6

Shore plover back on mainland

Andrew Trevelyan

| THIRTEEN New Zealand | shore plover, one of the world’s rarest wading birds, are being successfully reared at the | National Wildlife Centre at | Mount Bruce. Early last century the plover was common on rocky coastlines and estuaries around the | country but the spread of wild | cats, ship rats and other preda- | tors soon led to its demise. By | the 1880s the shore plover was | extinct on the mainland and it | is now limited to the remote, | predator-free Rangatira (or South East) Island in the | Chathams where less than 120 survive. | Seventeen shore plover eggs | were transferred to Mount | Bruce late last year in a bid by | DoC to raise sufficient birds in captivity to establish a second | viable population on a suitable | predator-free island. Fourteen of the eggs successfully hatched | and progressed well, although | one chick died, apparently through stress. | Ideally, 20-30 pairs will be ‘| required to establish a new | population as insurance against | a disaster, such as the introduction of rodents, eliminating the

single population remaining on Rangatira Island. Previous attempts to transfer birds to Mangere Island in the Chathams during the 1970s were thwarted by the strong homing instincts of the shore plover. All transferees either returned to Rangatira Island — one was even back on the island before the Wildlife Service team returned — or disappeared, and it became clear that a new population would have to be raised in captivity. Mount Bruce staff have experimented with shore plover eggs in recent years to gain the necessary expertise for this large hand-rearing exercise. Conservation officer at the Wildlife Centre Hilary Aikman believes the experience proved critical in two areas. "In the past we have tended to take eggs at an early stage of incubation. In that way the pairs would often renest so the population in the wild should be unaffected. But

these eggs had a low success rate. We found the success rate was higher when we took shore plover eggs at a more advanced stage of incubation, and some pairs still re-nested." The chicks were started on live aquatic invertebrates, before being fed other insects, mainly meal worms and wax moth larvae. Chopped and soaked "Go-Cat", and poultry feed were on the menu before the chicks took to the staple diet of waders at Mount Bruce, vitamin-enriched ox-heart, garnished initially with juicy maggots. In less than a month the chicks had reached their adult body weight (60 grams) and were well feathered. A short time later they were released into outdoor aviaries. At present the plovers are being observed to see whether any pairs form this spring, although pairing doesn’t usually occur until the second year. Staff will take care to make sure that chicks from the

same clutch do not pair up. Hilary expects it will be five to ten years before the National Wildlife Centre breeding programme will have enough birds to establish the second population on a predator-free island. Even mature birds are susceptible to predators. There was a grim reminder of that in the early 1980s when two mature shore plover, hatched and raised at the Otorohanga Zoo, were killed when a rat found its way into the aviary. Shore plover once lived on rocky shores, beaches and river mouths throughout New Zealand, but on Rangatira Island the birds have also settled on salt-swept turf among herbaceous plants. The coastal habitats of predator-free islands will be closely studied before the establishment of a second population is considered. Possible candidates are Mana Island, or Motuora Island in the Hauraki Gulf.