Call rate behaviour of brown kiwi (Apteryx mantelli) and great spotted kiwi (A. haastii) in relation to temporal and environmental parameters

Rogan Colbourne, Andrew Digby
unpublished
DOC Research and Development Series 348 Call rate behaviour of brown kiwi (Apteryx mantelli) and great spotted kiwi (A. haastii) in relation to temporal and environmental parameters Abstract Call rates are often used to monitor populations of cryptic species such as kiwi by providing indices of abundance to determine if a population under study is increasing, stable or declining. Observations using human listeners are limited by biases such as variation in hearing ability and fatigue. Therefore
more » ... the development of remote recording technology provides an opportunity to collect a great amount of data at little cost and effort. Call rates can also provide insight into kiwi behaviour. To gain a better understanding of how temporal and environmental conditions influence kiwi call rates, we deployed automated acoustic recorders at six sites-five inhabited by brown kiwi (Apteryx mantelli) and one inhabited by great spotted kiwi (A. haastii). Frequency of calling was clearly related to the breeding season for both species, but the pattern of calling was highly variable between sites and sometimes between years within sites. Brown kiwi call rates peaked in the first 10-40% of the night whereas great spotted kiwi call rates peaked in the second half of the night. Moonlight had no significant effect on male call rates at any site but had a significant effect on brown kiwi females at Whanganui and great spotted kiwi females at Saxon. At all sites, call rates were lower during high winds and heavy rain. Inter-seasonal variations in factors such as the quality of the previous breeding season or environmental conditions (e.g. summer droughts) could affect the ability of males, in particular, to recover to maximum breeding condition, which could, in turn, impact on call rates. Based on these findings, we recommend specific times at which kiwi call rates could be recorded to make monitoring more efficient and reliable. Because of the inherent natural variation in call rates, and the fact that chicks and juveniles rarely call, monitoring by calls is still too crude a method to determine an accurate density of a kiwi population.
fatcat:y7rpxt6bxjcprgljqpnvvmhzsy