Category Archives: Seychelles Warblers

59 Seychelles warblers from Cousin find a new home on Fregate

On 7 and 14 December, 59 Seychelles Warblers (Timerl dezil, Acrocephalus sechellensis) were transferred from Cousin Island Special Reserve to Fregate Island Private thanks to a Nature Seychelles-led initiative. The transfer was carried out to start a new breeding population on Fregate Island, making it the fifth island in Seychelles to hold this charming little bird with a story that reads like a fairy tale. The  operation involved a team from Nature Seychelles, the Seychelles Warbler Research Group,  and Fregate Island and the activity was funded by Disney Conservation Fund project  to Nature Seychelles. Birds were transferred using what is called the “hard release” method;  they were captured in the morning, transferred by Helicopter Seychelles and were released on Fregate by afternoon of the same day.  Read more about the translocation on our website: The most amazing conservation success story in Seychelles

David Wright was part of the translocation team.  Here he tells us what it was like to be part of this exciting conservation endeavour.

I’m a PhD student from UEA, in the UK, studying conservation genetics of the warbler. Am part of the Seychelles Warbler Research Group – a collaboration between the universities of East Anglia and Sheffield in the UK and University of Groningen in the Netherlands and working with Nature Seychelles for a number of years. The translocation of these special little birds to Frégate Island has been a fantastic opportunity for me to get involved directly in conservation at every stage of the process. It has enabled me to fulfil a lifelong ambition working in conservation.

My role has involved working both on Cousin, monitoring the population before the translocation and catching the birds to be moved, and on Frégate during and after their release. Working on a small tropical island is wonderful but often difficult; hiking up and down hills, scrambling over glacis and through mangroves in the tropical heat, carrying 45 mist nets and poles for catching birds around the island, with the ever hungry mosquitoes trying their best to drain you of blood…

Definitely not the ‘tropical holiday’ my friends back home thought it was! However, it’s not all hard work, and sitting on the beach watching the sunset with a cool drink in your hand is worth a million mosquito bites. The Seychelles is a beautiful place to work, particularly nature reserves like Cousin which offer such amazing wildlife experiences that it can be difficult to remember you have a job to do!

One of the main highlights of the translocation for me was the helicopter transfers to Frégate. What an amazing place to take your first ever helicopter flight! Seeing the coral reefs, the islands of Praslin, La Digue, Felicité and Marianne looming up from the turquoise blue ocean, Frégate island hazy in the distance awaiting the arrival of its new inhabitants – it’s a view I won’t forget in a hurry!

Dave releasing a warbler on Fregate

Dave releasing a warbler on Fregate courtesy of Paul Nixon

Releasing the birds during a translocation is perhaps one of the most fulfilling parts of the process and being directly involved in that was truly an honour. All the months of planning and hard work were worth seeing each and every warbler shoot out from its transportation box and into its new forest home.

From my experience during the translocation, I’d say the key ingredient is having a good, knowledgeable team. It’s critical you can work together and rely on each other, focussing your skills and effort to achieve your objectives. Being part of this fantastic translocation team is something I am really proud of and will look back on in years to come. Everyone brings their unique attributes and skills to the group and you really feel a part of something special. Overall, the translocation has been a phenomenal experience; the excitement, fun, anxiety, stress, hard work, sense of fulfilment and achievement – it’s been an emotional rollercoaster and an opportunity of a lifetime to be involved in something positive for conservation.

The translocation team by Dave Wright

The translocation team on Cousin by Dave Wright

Bird ringing on Cousin

Ringing is delicate work and ringers need training

Ringing is delicate work and ringers need training (Dieter Oschadleus)

From 18-23 September 2011 Dieter Oschadleus from SAFRING (South African Bird Ringing Unit) was on Cousin Island Special Reserve conducting training on ringing birds for the island’s wardens. Ringing and releasing birds is delicate work and ringers need skill and experience.The training was mostly on mist-netting of seabirds and land birds, a method used in bird ringing. A total of 478 birds were caught and ringed including recaptures. Riaz Aumeeruddy, Nature Seychelles Science and Conservation Coordinator was at the training and we took the opportunity to ask him a few questions. Following are his answers.

Why do we ring birds?

There are different reasons for ringing birds. One is to be able to identify birds individually in a population, usually using a combination of different coloured rings. This is what is done on Cousin with the endemic Seychelles magpie robin and the Seychelles warbler, where each bird is colour ringed. Usually most ringing programs involve only putting a metal ring with a unique ID on one of the legs of a bird. This will allow, if the bird is recaptured, to get information on its movement (on the island itself or inter-island), on its longevity (eg. a Seychelles fody ringed in 2002 on Cousin was recaptured during the training course, showing the the bird lives at least 9 years, information on the longevity of the Seychelles fody has never been published before) and social associations. Bird ringing can help answer a number of questions relating to causes and factors contributing to population movement, dynamics and behaviour.

Which types of birds do we ring?

On Cousin, we systematically ring two species of land-birds: the magpie robins which are ringed by the Cousin staff, and the Seychelles warblers that are ringed by the scientists from the warbler research group. Ideally all the birds of these two species are ringed, to know the exact population, and the territories in which they live on the island. Other landbirds are ringed for specific projects; the Seychelles fody was ringed on Cousin by a student who was doing her PhD on that species. Some species of seabirds are also ringed on Cousin, for example the White-tailed tropicbird and the Lesser Noddy are ringed during study of their breeding success (parents and chicks are ringed when they are on the nest).

A ringed Seychelles warbler (L, Cas Eikenaar) and magpie robin (R, Glenn Jackaway)

A ringed Seychelles warbler (L, Cas Eikenaar) and magpie robin (R, Glenn Jackaway)

What do the different colors mean?

Colour rings are used in a unique combination (2-3 rings) which helps identify each bird. For the  magpie robin, 1 colour ring is attached to the right leg to identify the island (eg. Cousin uses a Red ring) so if a bird flies from one island to the other, we can know from which island it is from, and 2 colour rings are attached to the left leg to identify the bird. With this system, the whole genealogy of a bird can be determined. For the warblers, 1 colour ring is used to identify the year the bird is ringed, and 2 colour rings for identifying the bird.

What was the outcome of the exercise

Four wardens, the science officer and myself attended the training course. All the participants received certificates. We need to thank Dieter Oschadleus from SAFRING for conducting the training, and the warbler team (Martijn Hammers, David Wright and Sjouke Ann Kingma) for their assistance during the course.

The Lesser noddy was the most ringed species

The Lesser noddy was the most ringed species (Dieter Oschadleus)

Thanks Riaz.

Dieter has also reported on this ringing exercise here and has provided a table of the species and numbers ringed.

Why are female warblers unfaithful?

Why does female infidelity occur so frequently throughout the animal kingdom? A 10-year study from the University of East Anglia seems to have an answer. It shows that Seychelles warblers (Timerl Dezil) may increase their offspring’s survival through their infidelity.

Although in many animals females may pair up with a specific ‘Social’ mate who helps raise the pairs’ offspring, DNA fingerprinting studies across a wide range of animals reveals that offspring may often be sired by other males. What has perplexed scientist is why females engage in such infidelity – what is the benefit of being fertilised by these other males – males which do not contribute towards raising the offspring.

Despite being apparently monogamous and pairing with the same male for life, female Seychelles warblers often prefer to be fertilised by other males, and this appears to increase the genetic quality of their offspring.

Seychelles Warbler mum and chick by Cas-Eikenaar

Seychelles Warbler mum and chick by Cas-Eikenaar

The study has shown that these extra-pair fertilisations can result in a higher diversity of specific genes which detect disease and trigger an immune response in offspring. As a consequence, the offspring survive longer probably as a result of having greater resistance to a wider range of diseases.

The research ‘MHC-dependent survival in a wild population: evidence for hidden genetic benefits gained through extra-pair fertilisations’ has been led by Dr David Richardson (UEA) and is published  in the Molecular Ecology journal. It was conducted with the University of Sheffield, the University of Groningen and Nature Seychelles and used the warbler population on Cousin Island.

Since 1997 more than 97 per cent of warblers on Cousin were ringed, blood sampled, and their breeding attempts followed. The researchers monitored the fate of 160 birds hatched on the island between 1997 and 1999, over 10 years.

They found that females paired to males with a low diversity of disease-detecting genes (known as major histocompatibility complex or MHC) elevate gene diversity of their offspring by gaining extra-pair fertilisations from males with higher diversity. This extra pair fertility was found to be common – accounting for 40 per cent of offspring.

Importantly, the offspring born as a result of this female infidelity have higher genetic diversity at these disease-detecting genes than they would have had if sired by the cuckolded pair male.

However they were not found to be higher than the population average.

The researchers then found a positive association between diversity of MHC genes and juvenile survival. A higher than median MHC diversity was found to increase lifespan more than two-fold.

Dr Richardson said: “We first tested whether extra-pair offspring have a survival advantage compared to within-pair offspring. Then we tested whether there are genetic benefits to the patterns of the MHC-dependent extra-pair fertilizations observed in this species.”

“We did not find any evidence for genetic benefits of extra-pair fertilisations per se, as on average extra-and within-pair offspring survived equally well.

“However, by not being faithful to a pair male with low MHC diversity, females are ensuring that their offspring do not end up with below average levels of MHC diversity and therefore lower survival.

“We have shown that the association between survival and MHC diversity levelled off with increasing diversity, so choosing males with above average MHC diversity would not have resulted in any additional fitness benefits for the offspring.”

“One thing that remains unknown however, is what mechanism drives the patterns of MHC-dependent extra-pair mate choice. Experiments are needed to determine whether females actively choose more diverse MHC males or whether other factors like male-male competition or sperm competition play a role.”

The story of Cousin on You Tube

Here is a YouTube video courtesy of Birdlife International called “The Story of Cousin Island”. The video was made during celebrations for the 40 anniversary of Cousin Island. Cousin Island was purchased by BirdLife in 1968 to save the last remaining population of Seychelles Warbler. 40 years later, according to Birdlife, “warbler numbers have risen by 300%, and the island has been transformed from a coconut plantation to a profitable Nature Reserve which greatly benefits local people and global biodiversity.

[kml_flashembed movie="http://www.youtube.com/v/CJeAmmUD7Jo" width="425" height="350" wmode="transparent" /]

With thanks to Birdlife.