When talking about the concept of a predator free Rakiura, one of the comments that we often hear is that there is no need for this work as the birds are doing fine. For those who spend a lot of time visiting sites outside of Halfmoon Bay, they would be well aware of just how incorrect this statement is. For most of the island, the birds are disappearing. In fact, my experience would be that if you exclude Halfmoon Bay and Ulva Island, then Stewart Island has less birds than most forested mainland sites.
To try to demonstrate this dramatic loss of birds, an acoustic survey of forest birds was completed at five sites about Stewart Island over the last month. The survey was completed for the Predator Free Rakiura Governance Group.
Five sites were selected for survey. Ulva Island represented a pest free environment. The Dancing Star site represented a fenced and predator controlled environment. Ackers Point represented the township, while Port William and North Arm represented areas where no long-term predator control has occurred.
Ten digital acoustic recorders (ARs) were deployed at each of the five sites between January 19 and 21. They were then collected approximately 10 days later. The ARs were programmed to run for 10 hours each day from 04:30 to 14:30. They were deployed at > 200 m intervals along predator control network tracks for ease of retrieval. In three instances (Port William, Dancing Start and Ackers Point) we sampled most of the available habitat. At the other two larger sites (North Arm and Ulva Island) the recorders were deployed in similar clusters to the three small sites. There was a five day period that all ARs we simultaneously recording (22nd – 26th) and we analysed 5 minute sessions after the dawn chorus (06:30 – 07:30), giving a total of 2580 samples.
Initial results analysed for kakariki indicated that over a five consecutive morning period kakariki were significantly more likely to be detected at the Dancing Star and Ulva Island Sites where pests are either absent or maintained at very low densities.
These are preliminary results only. The large number of samples will take a while to work through and full results will be detailed in the next SIN.
ACOUSTIC RECORDER (AR) SITES RAKIURA , JANUARY 2015.
PROPORTION OF DETECTION OF KAKARIKI PER 5-MIN SAMPLE INTERVAL FROM ALL SURVEY DATES FOR EACH SITE.