(Collecting body measurements and other data is routine while monitoring the Seychelles Warbler; file photo by Martijn Hammers)
It is one of the most studied bird species in the world, definitely the most researched species in Seychelles and the only bird whose status has been downgraded from Critically Endangered to Near Threatened in the IUCN Red List of endangered species through direct conservation action. The Seychelles Warbler was the reason Cousin Island Special Reserve was purchased nearly fifty years ago by BirdLife International then known as International Council for Bird Protection (ICBP).
There were only 20 individuals of this endemic bird left in the Seychelles, and they were only found on Cousin. Now there are over 3,000 birds spread over five islands owing to conservation action by Birdlife International, Nature Seychelles and island partners.
Cousin Island, which is now managed by Nature Seychelles (BirdLife in the Seychelles) was transformed from a coconut plantation and through rigorous conservation work over the years is now just about back to being the natural wildlife habitat it was before the first human settlement on the island.
But the work did not stop there. For decades, an army of researchers have visited Cousin at least twice a year to monitor the warbler population, and record and analyse an array of data collected.
Recently, in a three month period, between 22nd June and 19th September 2016, a set of researchers who form part of the Seychelles Warbler Research Group conducted field monitoring and analysis of the Seychelles Warbler on Cousin with the aims of carrying out a census of the species’ population on the island and count their survival and condition; for the birds with no identification rings, these were caught and ringed; and to observe and record the breeding attempts on the island.
Seychelles Warbler – once one of the world’s rarest birds (file photo by Martijn Hammers
The fieldwork was a long term partnership of researchers from the Universities of East Anglia and Sheffield in the UK, and the University of Groningen in the Netherlands and Nature Seychelles. The fieldwork was led by Professor David Richardson, Jan Komdeur, Terry Burke and Dr. Hannah Dugdale.
Through sightings in the forest and paths, as well as listening out for their various calls and sounds of them foraging, the researchers were able to locate the warblers in different territories around the island which number between 110-115 at any given time. For those that are ringed, they were able identify each individual by their unique set of rings around their left and/ or right legs. During this monitoring period, 28 birds were newly ringed.
The researchers reported that the warbler population on Cousin, although recovering, was still below average. Whereas there are usually approximately 320 individuals on Cousin, the census indicated that the population was down to around 254 individuals. This was attributed to a combination of unusually heavy rain and mass fruiting of the invasive pisonia tree which get stuck on birds’ feathers, causing them to be immobile, unable to fly and therefore can’t feed, thus causing them to die of starvation.
Other information collected during the June to September fieldwork included external measurements of the 81 birds that were captured in mist nests; a small blood sample for DNA testing and assessment for disease infection. The researchers now await the results of the blood samples that are currently being analysed in a laboratory in UEA.