Introduced birds successfully eradicated from Assumption! |03 April 2017

After three years of intensive eradication efforts and two more years of not seeing a red-whiskered bulbul or Madagascar fody on the island of Assumption, the Seychelles Island Foundation is delighted to report that the eradication of these introduced species has been successful!

The two invasive alien bird species were introduced to Assumption in the 1970s from Mauritius. The presence of these introduced species on an island only 28km from Aldabra was highlighted as early as the 1980s as a significant potential threat to Aldabra’s native birds. Aldabra, at the time, was one of the largest tropical islands in the world on which only native bird species occurred.

Funding to start an eradication programme for both species on Assumption was finally secured in 2010 from the European Union, co-financed by the Seychelles Island Foundation (SIF). Preparation work and trials of methods started on the island in late 2011 and the eradication effort was launched in early 2012.

Three years of permanent presence on the island by an SIF team of between two and 10 staff followed, with more than 30 different staff, volunteers and students being involved in the eradication activities at some point. The dominant method of bird capture shifted from mist-netting at the beginning of the project to mainly shooting after the mid-point, as the density of the birds dropped and the remaining birds became ever more wary. The last year of the project was the most difficult, with dedicated staff relentlessly pursuing the last handful of highly sensitised birds. At this late stage the team could spend up to several weeks targeting each individual, so every single bird successfully eliminated was a cause for quiet celebration and relief.

More than 5000 red-whiskered bulbuls were targeted and the last of these was shot in December 2014. Over 3200 Madagascar fodies were eliminated, with the final bird shot in January 2015, but it was not known at the time that this was the last bird so three further months of intensive continuous observations were required to convince the team that there were unlikely to be more fodies on the island.

Three major follow-up trips to Assumption have been carried out since then, with no indication of either species. Multiple shorter visits by Aldabra staff transiting Assumption have also occurred during this time with all eyes trained for any signs of the introduced birds. After two years with no traces of red-whiskered bulbuls or Madagascar fodies on Assumption, the SIF is at last confident that the eradication can be considered a success.

Early on in the Assumption eradication efforts, both introduced species were also found for the first time on Aldabra, validating concerns about their presence on Assumption, and leaving SIF with no choice but to start another expensive eradication programme as soon as possible. Fortunately,

Unesco emergency funding was quickly secured to partially support these new efforts on Aldabra, and eradication work and research were conducted on both islands in parallel for three years.

The single red-whiskered bulbul on Aldabra was eradicated very quickly. Dealing with the greater number of Madagascar fodies, however, was more complicated, especially after research confirmed SIF’s fears that they were hybridising with the endemic Aldabra fodies. Genetic research also showed that the Madagascar fodies on Aldabra originated from the Assumption population and that their presence on Aldabra pre-dated the eradication efforts on Assumption.

After three years of eradication activities under challenging circumstances, the SIF team has now eliminated all of the known Madagascar fodies on Aldabra and it is in the follow-up phase of monitoring to confirm their absence.

Aldabra, along with Assumption, should once again be on its way to becoming free of introduced birds, and this time with minimal risk of new introductions.

After this lengthy eradication mission and innumerable unexpected complications along the way, it is with enormous relief, and sincere gratitude to its partners, the Islands Development Company and Island Conservation Society, and its funders, the European Union, that the SIF is able to announce the successful eradication of both red-whiskered bulbuls and Madagascar fodies from the island of Assumption.

Although both species are common across the Western Indian Ocean islands and have been controlled elsewhere, the SIF is not aware that either species has been successfully eliminated from any other island and believe that this eradication represents a world first for invasive species management.

The SIF would also like to thank everybody who has been involved in this huge eradication effort:  consultants, team leaders, long-term staff, hunters, students, volunteers, Aldabra staff, all head office staff and everyone who was part of the team and helped to secure this remarkable achievement.