First confirmed death of adult Tristan albatross due to house mice
The two ‘round-island’ counts that we do as the Overwintering Team on Gough Island are usually one of the highlights of our year. We go out in January and count the adults sitting on their nests (or occasionally pairs of Tristan albatrosses still rekindling their bond after more than a year at sea), and then return 10 months later to count their chicks as they prepare to fledge. The job takes several days and we have to camp across the island – it is a perfect opportunity to really get to know the place we call home for the year (though as you can see from earlier blogs – the weather isn’t always kind to us!).
In between times, we monitor the nests at two sites more closely – Tafelkop and Gonydale. These are closer to our main base in the south east of the island – just a few hours' hike away. It was here, a few weeks ago, when our team first spotted two nests with adults carrying awful wounds. Our hearts sank.
One adult was sitting on her nest, chick still beneath her. The wounds were deep and looked serious – much worse than the one seen on a different adult in 2018 which was suspected at the time (though not proven) to have been caused by mice.
When the team returned to the area next, our worst fears were confirmed – the wound of the adult seen sitting on her chick had proved fatal. Her body was found a little way from the nest. Later the island’s scavenging birds were taking advantage of this windfall.
This adult, the female of the pair, was one of the most experienced breeding Tristan albatrosses in the world, having been ringed as a chick on Gough in 1986. She was the second oldest breeding Tristan albatross known and had raised several chicks in her lifetime.
This is the first time on record that a Critically Endangered Tristan albatross adult has been killed by house mice. As the chicks (at their heaviest) are heavier than the adults, we knew the adult’s size was no protection against the mice. But whilst the chicks can’t fly away, the adults technically can – we had thought that this may be the reason mice seemed to leave them alone.
The death of each breeding Tristan albatross is a serious loss – in terms of the species’ survival it is an even bigger blow than the loss of a chick because they have to survive for around a decade before they can even start breeding.
Mice, like all species, change and adapt to their surroundings – so it has, perhaps, always been a matter of time before the adults would be attacked. In some cases, like on Midway, new information between house mice has been seen to be transferred at speed. We can only hope that this behaviour is not yet widespread on Gough, and that the eradication attempt, now on the cusp of being implemented, is successful.
As for what is left of these two nests… With only one parent now providing food, the chick of the dead adult might take longer to fledge and is likely to be in a weaker state, multiplying the threat from the mice and making it less likely to survive at sea. At our last check at the other nest, there was no sign of the wounded adult and the nest had failed.
Kim Stevens is RSPB Senior Field Assistant, Gough Island.
This year the RSPB and its partners will try to eradicate the house mice on Gough and make it a seabird paradise once again. The project was originally scheduled to go ahead in 2020, but the coronavirus pandemic meant the RSPB and the Tristan da Cunha government had to abandon these plans and airlift the team home. With the delays the project now has a significant funding deficit.
If you would like to help close this funding gap, you can donate directly to the restoration project at https://www.rspb.org.uk/join-and-donate/donate/appeals/gough-island/
Acknowledgement The Gough Island Restoration Programme is being carried out by the RSPB in partnership with Tristan da Cunha, BirdLife South Africa, the Department of Forestry, Fisheries and the Environment (South Africa), the Royal Zoological Society of Scotland, Island Conservation, Conservación de Islas, Manaaki Whenua - Landcare Research and BirdLife International. The programme is part-funded by the RSPB, the UK Government, the National Fish and Wildlife Foundation and other generous individuals and organisations.