mortality

Costs and benefits of aerial 1080 operations to Western weka (Gallirallus australis australis)

The impact of aerially applied 1080 poison on a Western weka (Gallirallus australis australis) population was assessed at Tennyson Inlet, Marlborough Sounds, between September 2010 and June 2016. We estimated mortality and the incidence of sublethal poisoning as a direct consequence of two aerial 1080 operations and examined the differences in nest success, chick survivorship and adult survivorship. Most weka in the treated block appear to have been sublethally poisoned but only one of 58 (1.8%) radio-tagged weka died as a direct consequence of 1080 application.

Making endangered species safe: the case of the kokako of North Island, New Zealand

The theory of population regulation predicts that threatened species are safest at high population numbers, partly because density-dependent compensatory mechanisms counteract unpredictable disturbances. We illustrate this principle using data from the endemic kokako (Callaeas cinerea wilsoni) populations in the North Island, New Zealand. First we calculate the fledging rate per female (production) necessary to stabilise the population and thereby the residual numbers of nest predators, namely ship rats and possums, which have to be achieved to reach this production.

Mortality of North Island tomtits (Petroica macrocephala toitoi) caused by aerial 1080 possum control operations, 1997- 98, Pureora Forest Park

Aerial poisoning operations with carrot or cereal baits are used to control brushtail possum (Trichosurus vulpecula) populations in New Zealand forests for ecosystem conservation and to stop the spread of bovine tuberculosis to cattle and deer herds on adjacent farmland. Although various measures have been implemented to reduce the incidence of bird kills, dead birds continue to be found after poison operations.

Costs and benefits of aerial 1080 possum control operations using carrot baits to North Island robins (Petroica australis longipes), Pureora Forest Park

Large scale aerial poison operations with 1080-carrot baits are used extensively to control possum (Trichosurus vulpecula) populations in New Zealand forests for ecosystem conservation purposes and to stop the spread of bovine tuberculosis. Although various procedures have been implemented to reduce the incidence of bird kills, dead birds continue to be found after poison operations.