Acoustic monitoring has detected small populations of toutouwai/robin at lower elevations near the coast for the first time.
While toutouwai are present in the upper parts of the park, they were heard as low as 200 m altitude near areas with lush bush like Cleopatra’s Pool near Torrent Bay, and Huffam Stream near Wairima/Bark Bay. One bird has been seen at the bottom of the Falls River track near Anchorage.
This is an encouraging sign that robin are beginning to move to areas of good habitat as rat numbers are reducing. Acoustic monitoring will be a valuable tool to measure the change in distribution of native birds.
Acoustic recorders are deployed in the breeding season between September and November, at 120 sampling points across the park. This allows us to get a good idea of the distribution of toutouwai/robin, titipounamu/rifleman, pīpipi/brown creeper, kākāriki and kākā.
While five hours a day was recorded, so far only 45 seconds from each morning and each evening have been analysed. The results appear to replicate results from previous human observer walk throughs and demonstrate high sensitivity. An advantage of acoustic recordings is that they don’t interfere with the behaviour of the birds, and they can be replayed and checked over time.
Scientific advisor Ruth Bollongino has been analysing the recording samples with the help of spectrograms. Ultimately technology will allow us to analyse data much faster, especially as filters and deep-learning classification models for automatic detection becomes better over time.
Ruth says her impression is that bird dispersal along the coast is not only driven by predator numbers, but also by habitat quality. “I found robin everywhere where we have lush, moist gullies and on adjacent ridges. Regenerating mānuka shrubs alone don’t seem to be very attractive.”
Our goal is to use the acoustic recordings to better understand broad, landscape-scale changes in distributions of birds.
