| Summary: | Introduced mammalian predators are responsible for over half of contemporary extinctions and declines of birds. Endemic bird species on islands are particularly vulnerable to invasions of mammalian predators. The native bird species that remain in New Zealand forests continue to be threatened by predation from invasive mammals, with brushtail possums (Trichosurus vulpecula) ship rats (Rattus rattus) and stoats (Mustela erminea) identified as the primary agents responsible for their ongoing decline. Extensive efforts to suppress these pests across New Zealand’s forests have created "management experiments" with potential to provide insights into the ecological forces structuring forest bird communities. To understand the effects of invasive mammals on birds, I studied responses of New Zealand bird species at different temporal and spatial scales to different intensities of control and residual densities of mammals. In my first empirical chapter (Chapter 2), I present two meta-analyses of bird responses to invasive mammal control. I collate data from biodiversity projects across New Zealand where long-term monitoring of arboreal bird species was undertaken. The projects cover a range of treatments including fenced sanctuaries, offshore islands, forests treated periodically and sites lacking significant mammal control. I found that New Zealand bird species exhibit complex responses to the varied and sustained management effort that has occurred across New Zealand’s landscape in the last fifty years. Some species show significant positive outcomes to control, notably the larger endemic species, while others, including highly endemic species, consistently decline after control. In Chapter 3, I estimate the responses of bird populations in the central New Zealand region to changes in ship rat densities. I collaborated with scientists from the Department of Conservation (DOC) and Greater Wellington Regional Council and collated biodiversity data from four restoration projects located across the central New Zealand ...
|
|---|