Eaten to Extinction: another devasting year for MacGillivray’s Prion

Mice attacking 20-day old MacGillivray’s Prion (© Ben Dilley)

In another devasting year for the endangered MacGillivray’s Prions on Gough Island all but one chick have died this year at a monitoring site, putting the long-term future of the species in jeopardy.

Only one chick is still alive out of 50 monitored nests, with invasive mice eating many of the newly hatched chicks.

Mice were inadvertently introduced to Gough Island in the 19th century, most probably by sealers. The mice have since adapted to feed on a nutritious and plentiful food source – the seabirds. These mice are now a very real threat to the eight million breeding birds who live on Gough, including the Endangered MacGillivray’s prion and the Critically Endangered Tristan Albatross. Invasive rodents have already been responsible for the local extinction of MacGillivray’s prions from two French Southern Territory islands in the Indian Ocean.

The RSPB has been monitoring a group of these burrow-nesting nocturnal birds in a cave since 2014. The survival rate in this cave is seen as an indicator of how the birds are doing all over the island.

It is thought that these mice are largely responsible for the collapse of MacGillivray’s prion populations on Gough Island from about 3.5 million pairs in 1956, to 175,000 pairs in 2020. (© Roelf Daling)

Since 2017 only one chick has fledged at this site. This is due to mice eating the chicks, or parents deserting the eggs because they themselves are being attacked by the mice.

A new paper, published in the journal Animal Conservation on Monday 15 February, predicts that these birds will continue to decline by 9% each year if mice remain on the island, with a 31% chance that they will go extinct on Gough by 2057. If the mice are eradicated, however, there is a high likelihood that the population will stabilise and slowly recover.

The RSPB, in partnership with Tristan da Cunha and others, are undertaking an ambitious project this year to restore the fortunes of millions of seabirds by eradicating every single mouse from Gough Island. This project was originally projected to take place in 2020 but was delayed due to the coronavirus.

Kim Stevens, RSPB’s Senior Field Assistant on Gough Island, said: “It’s so upsetting that, yet again, so many of these little chicks have died. MacGillivray’s prions only lay one egg a year, so for that one egg to never make it to adulthood, year after year, is just heart-wrenching. Even the precious chick which is still alive still has seven weeks to go before it can fly so there’s a very small chance it will make it. But, with the restoration project so close at hand, I have every hope that we will soon be able to make this island a global haven for seabirds once more, helping to revive our world.”

For more information about the project, or to donate, please visit the Gough Island website page.


20 February 2021

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