What they do in the shadows : habitat utilisation and diet of brown kiwi (Apteryx mantelli) adults within a high-density island population : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Science in Ecology, Massey University, Palmerston North, New Zealand
Exploring the complex interactions between an animal and its spatial environment can
reveal much about its biology and behaviour and identify strategies to improve future
management. Despite this, surprisingly little research has been undertaken in this field in
respect to one of New Zealand’s most iconic endangered species, the brown kiwi (Apteryx
This thesis aims to produce the most comprehensive report to date of brown kiwi spatial
behaviour, investigating the habitat utilisation of brown kiwi adults within a high-density
population while they are active at night and when roosting during the day. Additionally, the
study examines how habitat utilisation varies, and explores the likely drivers of brown kiwi
spatial behaviour including food availability, social/reproductive cues, population
demographics and environmental variables.
Forty seven radio-tagged brown kiwi adults were tracked across a 1.2km2 study site on Ponui
Island from March 2013 to February 2014. The utilisation of major habitat types (forest,
scrub, pasture and swamp) by each bird was measured, plotted upon a generated habitat
map, and compared to predicted rates based on habitat availability to assess habitat
selection. To assess habitat selection while foraging, brown kiwi were tracked at night using
radio telemetry and their positions estimated using a triangulation methodology. Exact bird
locations were also recorded during the day to evaluate their roost habitat selection. Roost
sites were also classified into four different types of roost (tree burrow, soil burrow, surface,
swamp site). Brown kiwi faecal samples were collected over this time and compared with
pitfall trap samples to analyse diet and identify spatial patterns in foraging behaviour.
As hypothesised, brown kiwi selected forest habitat most often for both foraging and
roosting, also choosing the more structurally stable tree and soil burrow shelter sites. Other
habitat types were utilised much less than predicted, though rates varied between seasons,
gullies, demographics and behaviours. Pasture was identified as seasonally important for
brown kiwi, utilised increasingly by study birds over summer and autumn when foraging.
Additionally, a relationship between their spatial behaviour while foraging and while
roosting was recognised for the first time, suggesting that these behaviours are not
independent. Invertebrate availability was identified as the primary driver of brown kiwi
spatial behaviour, with foraging behaviour trends closely matching nocturnal spatial
behaviour. Social and breeding behaviours were discussed as other potential drivers, though
further research is required to fully understand these relationships. Research findings
confirmed that brown kiwi have an opportunistic diet, appearing to select those
invertebrate groups that provide the highest protein input more often in their diet. Foraging
strategy changed between seasons and locations, likely driven by a combination of changing
invertebrate lifecycles, environmental conditions and dietary requirements.
This study has improved our understanding of brown kiwi spatial behaviour, introducing
new information and refining previous knowledge. The findings provide valuable
information for managers as they work to conserve remaining brown kiwi populations, and
will become increasingly relevant in the future as population densities begin to rise.