Individual study: Translocation methods for shore plover Thinornis novaeseelandiae, The Chatham Islands, New Zealand
Aikman H., Davis A., Miskelly C.M., O'Connor S. & Taylor G.A. (2001) Chatham Islands threatened birds: recovery and management plans. Department of Conservation. Threatened Species Recovery Plan: New Zealand shore plover, 36-46
The shore plover Thinornis novaeseelandiae is a rare, endemic New Zealand bird listed by the Department of Conservation as 'nationally critical'. Previously more widespread, at the onset of this study it was restricted to one island, Rangatira in the Chatham Island group, 800 km east of New Zealand. The population of an estimated 130 individuals survived because predators (e.g. rats, cats) were never released on the island. Being so restricted in distribution the shore plover was vulnerable to accidental introductions of predators, and chance disaster events. Previous attempts to translocate this species to Mangare island (after predator eradication), also in the Chatham Islands group, have been unsuccessful. Complicating issues are that adult birds form a strong bond with their natal site, and birds are very social, requiring other shore plovers to be present in the vicinity before they establish a population. Two of the conservation methods for this species, and their merits, are described here.
Hard release: This technique was used in the 1980s in the first attempts to translocate shore plover. Adult and juvenile birds were caught in mist nets (fine semi-transparent nets designed to catch birds), put into carrying containers, shipped to Mangare Island (free of introduced predators) and released. Three attempts were made, each of 10-15 birds.
Captive breeding & soft release: A captive-breeding programme began in 1991 at Mt Bruce Wildlife Centre, Wairarapa (North Island, New Zealand). Eggs from wild parents were taken off Rangatira island and transferred using a transfer box (essentially an oversized lunchbox approx. 20 x 30 cm. with a small heating element, small fan and a thermostat to maintain egg temperature). Having survived transportation, the eggs were then placed in incubators until hatching. Thereafter the chicks were housed in a brooder and hand fed on a diet of small, mostly aquatic invertebrates. Chicks were then released into aviaries along with the other young birds. Aviary conditions mimicked their natural environment, being alluvial shingle with shallow freshwater creeks and wading habitat. Pairs formed and nests were made. Eggs were left to hatch in the aviary but monitored closely. Fledglings of 30-60 days old were then translocated to Mangare island, and released using a soft release method.
The soft release method is labour intensive and time consuming, but successful. It had been trialled for other species on inshore islands since 1993 and thereafter used for recovery of shore plover populations. Three translocation programmes were attempted, the first and third are reported here. Between 1993-1998, 75 fledgelings were released into an aviary on Motuora Island then released into the wild. None are known to have survived and were thought to have been either driven out or preyed upon by morepork Ninox novaeseelandiae (a native owl).
During the third translocation and release programme, a similar number of fledgelings were transferred to Mangare Island starting in 2002. Upon release there was 100% residency.
Hard releases: The hard release method was not a successful translocation method for shore plover. Most of the birds had returned to their natal island (Rangatira) before the boat arrived back there! However these early trials led to further investigation into methods of translocating social birds with natal site fidelity. Subsequently, the combination of captive breeding and soft release methods was adopted.
Captive-breeding & soft releases: Captive-breeding proved very successful. Taking eggs from the wild encouraged pairs to lay a repeat clutch and resulted in little impact on the breeding sucess of the only wild population. Hatching the eggs in incubators, and hand rearing of chicks enabled a 100% hatch success rate and 96% of birds survived to fledging. By keeping the young in aviaries, breeding pairs formed and the offspring could then be released at the new location.
The soft release method proved to be very successful. When they were released pairs settled easily as there were already established shore plover for them to socialize with. The population of shore plover on Mangere Island now numbers 15 adults. Mangere Island has only enough habitat to support about six breeding pairs so new potential release areas are being investigated at present.
Present population: As of 2005, there are 220 individual birds living in the wild and 20 birds in captivity. This represents a substantial increase in population (from 130 individuals) as estimated at the start of the project.
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