Naturally for Birds donates all profits to the Save the Gouldian Fund to support research and on-ground actions to help conserve wild populations of the endangered Gouldian Finch. In this series of articles we provide some information on the research projects being supported.
Finch Movements – how far do Kimberley finches move?
Save the Gouldian Fund’s biggest current investment is with Charles Darwin University in Darwin where we support a project seeking to quantify finch movements in the Kimberley landscape around Wyndham.
Researchers from the Movement and Landscape Ecology Lab at CDU lead by Prof Hamish Campbell and Dr Tara Crewe are tracking the movements of finches to better understand how often and how far they move, where they spend time, and how they respond to fire and seed distribution across the landscape.
The project is highly innovative in using tiny transmitters placed on the birds and receiving towers which detect the tagged birds as they move around the landscape. During the 2019 season the team completed the installation of a network of 21 receiving towers spread over a huge area around the Wyndham region.
One of the critical tasks was then to calibrate the array of receiver towers; that is, figure out how the signal strength from transmitter tags on the birds declines as the tag moves away from the tower. Using this information they can use the known signal strength of each detection to estimate how far a bird was from each tower. When a bird is detected by more than one tower at the same time, this information can be used to estimate the position of the bird.
To do the calibration a team member walked through the array of receivers with a tag in hand and flew a drone through the array with a tag attached. In both instances they knew the position of the tag at all times and could estimate how signal strength varied throughout the array and with distance from each tower.
The tiny 0.3gm transmitter tags were attached to a total of 166 birds through the year from May to November with 65 on Gouldians, 46 on Masked finches and 55 on Longtails.
The transmitters operate for at least three months and can be detected by the towers from a great distance. This huge effort and the data from the towers has generated some amazing data, revealing things we simply didn’t know before.
Between May and October the radio-receiving towers collected over 8 million unique detections of 162 tags with an average of over 50000 detections for each individual. Much more data will be collected from the tags applied in October which will continue to transmit through into January 2020.
This mark-recapture technique has been hugely successful. In the past such studies relied on recapture of birds with leg bands applied and only about 1.7% of rung Gouldians were ever recaptured. With the transmitter tags and towers the team has seen a phenomenal 92% “recapture” rate. Birds were tracked for between 1 and 153 days, with an average of 52 days between date of release and last detection.
To give an idea of how often some of these birds move between sites, the following plot shows how often an adult female Gouldian Finch (tag #123) moved between the Wyndham, King River Road, and Guda Guda sites between 25 June and 5 July 2019. She returned daily to King River Road – maybe she was nesting there? That’s quite a daily flight (several km) for a small bird.
Movements of another Gouldian female are shown below. She displayed another interesting pattern after she was tagged at Singh’s in early May. Soon after she moved many kilometres to the town of Wyndham and remained there until June 15, perhaps while nesting. She then begins to move on a daily basis, and is detected by three other widely spread towers moving back and forth.
In addition to mapping movements, the team are estimating home ranges and correlating this with habitat preferences. The map below shows how an adult male Gouldian Finch seems to have a core use area (red) that includes two areas of Wyndham town. This includes near the Caravan Park, where it comes for a drink daily at around 7:00 am or later between 3:00-4:00pm. It’s home range (white) covers a much larger area.
Finally the study allows comparisons of the movements of Gouldians, Longtails and Masked Finches. The results to date show that Gouldians are moving around the area much more than the other two species. They are almost certainly doing so to find food and it appears Gouldians are under more nutritional stress than the other locally abundant finches.
This project has generated a huge amount of data, with more to come, and then much analysis to turn that data into knowledge and allow a much greater understanding than we have previously had about how finch species utilise the Kimberley environment.
More updates to come as the research team is now preparing the outcomes for publication.