North Island brown kiwi (Apteryx mantelli) monitoring at Whenuakite: Trend comparison of observer and acoustic recorder collected call counts
|Title||North Island brown kiwi (Apteryx mantelli) monitoring at Whenuakite: Trend comparison of observer and acoustic recorder collected call counts|
|Publication Type||Journal Article|
|Year of Publication||2018|
|Authors||Stewart, P, Hasenbank, M|
|Type of Article||Full article|
|Keywords||acoustic recorders, applied monitoring, call count survey, detection probability, sampling precision|
Observer call count surveys are utilised throughout New Zealand to monitor kiwi populations. The development of affordable autonomous acoustic recorders by the Department of Conservation has enabled the collection of large quantities of digital data. Utilising call count data from the North Island brown kiwi (Apteryx mantelli) monitoring programme at Whenuakite from the 2010 and 2015 survey periods, a retrospective comparison between data collected by human observers and acoustic recorders was undertaken. Both survey methods indicated an increase in the number of kiwi calls per hour between the 2010 and 2015 surveys. The overall ratio of the number of calls per hour detected by acoustic recorders to those detected by human observers was 1:1.52. Results from the occupancy modelling indicated that the average detection probability for human observers was almost twice as high as that for acoustic recorders. Furthermore, increasing the number of sites for monitoring kiwi populations improved the associated level of precision of the derived occupancy probability estimates. Adjusting the survey design to the underlying characteristics of the kiwi population are therefore important to gain reliable estimates of their population trajectory.