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A flying start for Citizen Science in 2022: seabird monitoring at Rat Island

CCWA’s Citizen Science program for 2022 is off to a flying start!

For our first fieldtrip of the year, our team of trained bird-banders travelled to Rat Island in the Houtman Abrolhos. Known for its crystal blue waters and an abundance of sea life, the Houtman Abrolhos Islands consist of 210 islands located off the coast of Geraldton.

The aim of the trip: continue the investigation into the population dynamics of the threatened Australian Fairy Tern, and to document the recovery of seabirds following rat, cat and mouse removal from the island, which has been taking place since 2003. Rats and mice were eradicated in 1991 and 2018 respectively, and the cat last died in 2000.

A core component of the Rat Island seabird recovery research is the mark-release-recapture of Fairy Terns, which are banded under the Australian Bird and Bat Banding Scheme. Fairy Terns are caught at Rat Island during their post-breeding migration back to the Houtman Abrolhos Archipelago in the autumn. 

 (L-R) View of Wooded Island (Credit: Nic Dunlop) | Our amazing team of bird-banders: Alison Goundrey, Erin Clitheroe, Dr Nic Dunlop, Dr Claire Greenwell, Chris Lamont (Credit: Nic Dunlop) | A friendly sea lion the team met while off-duty! (Credit: Chris Lamont)

Reaching the island via light aircraft, our team of skilled bird-banders spent 3 nights on Rat Island.

By day, the island’s airstrip is used by airplanes, and by night, it’s a roosting site for the Fairy Terns – so this is where our team set up!

Over the course of the weekend, our team caught a total of 52 individuals. Of those, four were recaptures – birds that had been banded previously. These included one adult caught at Rat Island in December and another banded in April 2019. The other two were known-age juveniles, banded in December 2021 at a colony in Dawesville, around 500km south of Rat Island. Learn more about our other bird-banding operations here.

Head-bill length measurements and moult patterns were assessed. Post-nuptial adults were found to be moulting primary feathers 5–10. Juveniles were undergoing their basic moult, i.e. replacement of contour feathers, but as expected, no primary feather moult was observed. For more information on Fairy Tern moult, see our ‘Fairy Tern Conservation Guide’ in the resources section of our website.

Birds are tagged with a small, lightweight metal band on leg, their details recorded, and then released. The re-sighting and recapture of banded birds has provided important insights into the ecology and movement of the Fairy Terns, which are one of WA’s most vulnerable seabirds.

Dr Nic Dunlop first began banding Fairy Tern ‘runners’ (pre-fledgling juveniles) on Tern Island, Safety Bay in 1997. A total of 40 birds were banded and re-sightings of three of these now 20+ year old birds have been made in the past three years. The longevity record for the Australian Fairy Tern is 24 years of age, breaking the previous year’s record when one of the Tern Island-banded birds was resighted at a breeding colony in January 2021 and successfully raised a chick.

(L-R) Claire, Alison, Nic and Erin setting up mist nets (Credit: Chris Lamont) | A juvenile Australian Fairy Tern (Credit: Erin Clitheroe) | Erin and Alison banding and measuring birds before release (Credit: Nic Dunlop)

When not banding, the team spent their time identifying the locations of Little Shearwater and Wedge-tailed Shearwater burrows, surveying birds on the island, and searching for any signs of mouse activity.  

CCWA’s mice-removal program in 2018 appears to have been successful, with no evidence of the mammals observed on Rat Island for 4 years. After two years of planning and enormous volunteer effort to install the bait stations across the island, this is an excellent result. The removal of mice has, potentially, had a positive effect on the granivorous (seed-eating) Brush Bronzewing population, with good numbers seen across the island in April 2022. The number of Little Shearwater and Wedge-tailed Shearwater burrows also seems to be increasing with new sub-colonies observed in previously unused areas on the island.

Big thanks to Claire, Nic, Alison, Erin and Chris for carrying out this important research.

CCWA's Citizen Science Program is a research and monitoring program driven by volunteers and scientists to gather data and answer questions about real-world questions. You don't have to be a scientist to get involved - all you need is a healthy dose of curiosity, an interest in biodiversity and ecosystems, and some time to spare.

Signup now to receive on-ground Citizen Science updates and news in 2022.

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