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.
Nest success, the proportion of clutches resulting in one or more fledglings, is a key indicator for assessing the effect of management on bird populations. However, the figures reported for New Zealand populations are usually "apparent nest success", the number of successful nests divided by the total number found. Apparent nest success invariably overestimates the true success rate, and the degree of bias depends on the population and monitoring regime. Consequently, apparent nest success rates cannot be reliably compared.