House mouse (Mus musculus) use of vertical space and impact on bird nesting success

Prior to human arrival, New Zealand was dominated by birds that had evolved in the absence of mammalian predators. Early Polynesian settlers brought with them the kiore (Rattus exulans), which subsequently decimated many native species. Following this, Europeans brought ship rats (Rattus rattus), Norway rats (Rattus norvegicus), house mice (Mus musculus) and an array of other mammalian predators causing even more damage to the native flora and fauna. Present day conservation strategies seek to control or eliminate invasive predator populations to give the native birds a chance to recover. At Maungatautari – a pest-fenced reserve in the Waikato, New Zealand, mice remain as the sole invasive mammal following extensive eradication programmes. When left on their own, mouse populations are known to greatly increase. On some offshore islands in the South Atlantic and sub-Antarctic, their diet has been shown to include bird eggs and chicks, and on other islands they have used resources that were previously unavailable to them (by predator or competitive exclusion). Therefore, the aims of the present study were to examine how mice; (1) use vertical space in the presence and absence of other mammalian predators and (2) impact bird nesting success when they are the sole predator. Chapter Two examines how mice use vertical space in the presence and absence of other mammalian predators while also quantifying how other small mammals use vertical space. Tracking devices (that included chew tags) were placed at different forest heights within two separate patches of bush, one with only mice present (Maungatautari Sanctuary) and one where all pest mammals were present (Te Tapui Reserve). Mice were found to frequently use the lower (