WILDLIFE MONITORING
Monitoring is carried out to assess the effects of pest control on the native wildlife species we want to protect. Annual kiwi listening is carried out at night to assess kiwi populations and bird counts are carried out during daytime to assess other bird species. Volunteers do the monitoring.
Kiwi Monitoring
Kiwi call monitoring is carried out annually by volunteers and Department of Conservation staff sitting out at established listening points scattered throughout the Trust’s management area in Puketi Forest.
Listening is undertaken during May and June, when kiwi calling is at its peak, on fine calm moonless nights. Calls are recorded during the first two hours of darkness on four nights (a total of eight hours per site). By recording the time, direction, estimated distance and sex of each call, the number of kiwi calling within the area can be measured. Although not all birds call, a useful index of the kiwi population is obtained.
Juvenile kiwi don’t start calling until they are 3 or more years old, so the effects of predator control on breeding success are not immediately obvious.
Monitoring was first carried out in 2000, with further listening in 2004 and annually from 2006. There are 15 listening sites in the forest. Two are remote and are only monitored every few years. Results from the ten most regularly monitored sites are summarised in this graph.
There was a decline in call numbers from 2000 to 2004, which might reflect the effect of predation before the start of pest control. From 2004 to 2011, average call rates and the estimated number of kiwi calling increased by about 2.5 times. Numbers have remained similar since.
Native Bird Counts
The presence of birds active in the forest during daytime is monitored by experienced birdwatcher/ornithologist volunteers each autumn. 14 or 15 regular sites are recorded each year.
The standard 5 minute bird count is used, which involves sitting silently for 5 minutes and recording all birds seen or heard. It gives a measure of day-active bird abundance suitable for the assessment of trends over several years but is not precise and too much should not be read into minor variations.
Several factors affect the results, for example the weather during the second day of monitoring in 2017 was worse than forecast and far from ideal for observing bird activity. Recorded bird numbers were depressed that year as a result.
The table below shows the average number of birds per site of each species recorded in autumn bird counts from 2005 to 2019. A summary of these data is presented in the graph that follows.
Rat trapping began on the plateau in December 2005 and in the Te Tawa area in January 2008. The numbers of both native and introduced birds recorded have approximately doubled since rat control began. Most introduced birds are recorded close to the edge of the forest.
Autumn 5 minute bird counts – average number of birds per site
(15 permanent sites within core pest control area)
Autumn 5 minute bird counts – average number per site of native (9 species) and introduced (6 species)
