02 June 2011

High mortality rate for Tristan's rescued rockhoppers

Rockhopper penguins in the release
pool on Tristan da Cunha.
Photo by Katrine Herian/RSPB
TRISTAN DA CUNHA - Sadly, despite the valient efforts of the penguin rescuers, the overall mortality rate for the rockhopper penguins oiled by the wreck of the MS Oliva has been extremely high - the figure given by RSPB is around 88% for those birds that were moved to Tristan.

RSPB acknowledged this is a much higher mortality than in other oiling incidents, but hopes that lessons can be learned that will improve this figure should something similar occur. The extreme remoteness of the Tristan islands and the necessary delay (at least 6 days sail from Cape Town) in getting vital supplies and staff to the islands probably contributed to the low survival, as birds would have been consuming toxic oil from their feathers for more than a week before rescue was undertaken. 

The penguin rehabilitation project team continue to work relentlessly in all weathers, in an effort to secure the successful release of clean, healthy, waterproof birds. Around 25 Tristanians are still working full time with the penguins, and the entire community remains dedicated to seeing the remaining birds head out to sea as soon as possible.

On 21 May, a trial release took place, with the fittest 25 penguins released from the pen. Eleven of these birds returned to the release pen (one of them straight away), but all of these were found to be in good health and showed no signs of stress or weakness. With the relative success of the trial (there were no known fatalities) the rehabilitation team are now working on a plan to release a further 110 birds that are ready to go.

As at 23 May, there were around 380 penguins remaining in the rehabilitation centre on Tristan. These birds have gained weight well, but they will not be released until their feathers are in excellent condition, as sending them into a cold south Atlantic without their waterproofing intact would be disastrous.

All remaining wild penguins have now departed from the islands, and headed off to their winter feeding grounds. The true impact of this calamity on the population won't be known until the birds return to breed on the islands in August and September.

RSPB’s Brad Robson will travel to Tristan in September to assist the Conservation Department with their annual rockhopper census. Hopefully, some of the measures taken by the Tristan team, such as corralling penguins on land to prevent their exposure to oil, will have saved the lives of numerous birds.

The wreck of the MS Oliva remains in the water near Nightingale, and some oil is still leaking from the vessel. It is likely that winter storms will break the wreck up, and will disperse this oil, but the situation will be monitored for possible impact on returning birds.

So far, the insurers of the MS Oliva have paid for all the rehabilitation and clean-up efforts, and hopefully they will continue to act responsibly in the coming months and years.

There will, however, undoubtedly be some work that cannot be funded through insurance. One area where funds raised through the RSPB Nightingale Island Emergency Appeal can contribute will be ensuring that the people of Tristan da Cunha have sufficient resources on hand locally to deal with any future oiling incident rapidly and without awaiting supplies from Cape Town. The community now has significant expertise in penguin rehabilitation, and hopefully this can be shared with other South Atlantic islands (e.g. the Falklands and the French territories) to enable them to also mount rapid responses if an incident like this one occurs in the future.

Read related posts

Sources
Gaining weight, but not yet waterproof: penguins still need care, RSPB, 12 May 2011, BirdLife International
MS Oliva Tristan-based diary, Tristan da Cunha Association: accessed 1 June 2011

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