Completing the colour-wheel of Macquarie Island’s petrels from white-headed to grey we’re now on to blue petrels. Poetically, their scientific name Halobaena caerulea means “the blue sea-walker”. The first report of them is from 1900 when they were described as “exceedingly numerous”. Numbers plummeted through the 1900s until the species was extinct as a breeder on the main island. A handful of tiny populations were found surviving on offshore rock stacks in the 1970s. As a result of their massive decline they are treated as a threatened species under Australian federal and state legislation.
I’m looking at how the population is responding since the eradications, first of cats by 2000, and then rabbits, rats and mice in 2011–2014. The numbers won’t be crunched for some months yet, but already the apparent changes are remarkable. Blue petrels have recolonised the mainland and are expanding outwards from these first returning pioneers. Most dramatic are the scenes at North Head where colonies have spread from the tip to occupy available patches of tussock half way back along Wireless Hill. It will be a race to see if they make it to the Ham Shack before the station itself is moved across the Isthmus. Visiting at night, what have for decades been blank skies are now filled with a swirling mass of birds returning on dusk to the colony. They’re reforming their pair bond and renovating burrows during September before returning to lay eggs in October. At Green Gorge once silent slopes next to the Overland Track become a bubbling wall of noise after dark (visit the Xeno-canto Foundation website to hear the sounds of a colony).
Petrels return to land at night to avoid diurnal predators like skuas and kelp gulls. If you want to find them and get a handle on numbers you really have to join them at night, so September for me is about getting off station and out of the huts at night searching the coastline for the ghostly white flashes as a passing bird is lit up in the dark. Other expeditioners of the 71st ANARE are helping me visit some of our remote spots, and we’ve got more to come.