Swarms of bogong moths blanketing homes in Australia’s southeast are a sign the endangered species is recovering, authorities said on Saturday.

The moths, with a wingspan of up to 5 cm, have suffered years of steep population decline, shrinking their southern spring migration to caves in the Australian Alps. The journey can stretch up to 3,000 km.

But this year the moths have come back in force, with reports of insects invading backyards and homes along Australia’s east coast, including Sydney. “It’s really exciting to see this recovering population coming our way,” said Steve Whan, who represents the alpine area of Monaro in the New South Wales parliament.

In neighbouring Victoria, chief biodiversity officer James Todd said the jump in numbers is a positive sign for biodiversity. The moths support native wildlife like the pygmy-possum and pollinate eucalyptus trees.

Why it matters: one theory for the rebound is more rainfall in northern New South Wales, producing extra food for the insects’ larvae.