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28/06/2016 Invasive species

15 mangrove finch chicks successfully released on Isabela

The island of Isabela is now home to the third group of mangrove finch hatchlings.

Photograph of Jenny Vidler

Jenny Vidler

Former Communications & Membership Assistant at Galapagos Conservation Trust

Fifteen mangrove finches were released into their natural habitat in May of this year, thanks to funding from multiple sources including the Galapagos Conservation Trust, and a lot of hard work and determination from the Charles Darwin Research Station’s Mangrove Finch Project Team on the ground; the team spent six weeks camping in the field in order to provide round the clock attention for the fledglings.

Francesca Cunninghame©

Francesca Cunninghame©

The mangrove finch, a species endemic to Galapagos, is on the brink of extinction. The mangrove finch’s greatest threat is the presence of the parasitic larvae of the introduced fly Philornis downsi. The effects of the fly’s larvae feeding on the wild mangrove finch hatchlings has cause exceptionally high levels of mortality in wild nestlings. This has resulted in the drastic decline of mangrove finches, reducing the population to critical levels. It is estimated that there are currently only 100 individuals remaining, with fewer than 20 breeding pairs. While various control methods for Philornis downsi are being researched, the mangrove finch head-starting program began in 2014 as an attempt to immediately bolster annual fledgling success within the mangrove finch population.

To release the hatchlings, the birds were loaded into transport boxes aboard the Galapagos National Park Directorate (GNPD) vessel Sierra Negra and transported to Isabela from Santa Cruz. The birds were then kept within a specially designed aviary at Playa Tortuga Negra for three weeks. As a soft release, the captive reared fledglings were provided with natural substrates such as damp logs, bark, foliage, a thick layer leaf litter and mangrove roots in order to encourage foraging and to aid in the re-assimilation process.

playa tortuga map 5

Before they were released, all fifteen of the fledglings were fitted with miniature radio transmitters. The light-weight transmitters, weighing only 0.3g, were fitted to their base of their tails, which allowed the fledglings movements to be radio tracked for up to 18 days after their release.

On April 26, the aviary doors were opened and the birds were free to explore their natural habitat.

In the following days, essential information was transmitted back to the team, showing that the fledglings maintained similar dispersal and foraging behaviour to both wild-reared and captive-reared mangrove finch fledglings from the previous seasons. Monitoring efforts showed that the fledglings maintained similar dispersal and foraging behaviour to both wild-reared and captive-reared mangrove finch fledglings from the previous seasons. For the majority of the time, the fledglings stayed within the mangrove forest at PTN, and were found interacting with both adults and juvenile mangrove finches. Surprising results from the trackers showed the team that eight individuals travelled as far as 1.5km away from the aviary, crossing the surrounding lava fields to forage in arid zone vegetation. The transmitters were removed from the finches returning to the aviary.

Francesca Cunninghame©

Francesca Cunninghame©

The breeding season of 2016 was particularly challenging for the mangrove finches. The breeding season generally occurs until late April or May, however, this year no mangrove finch nesting occurred later than March due to the dry weather conditions. The shortening of the breeding season made the chances for reproduction slimmer than previous years.

Obtaining observations of juvenile non-breeding mangrove finches is exceptionally challenging due to their shy nature. For this project to succeed fully, the captive-reared birds must adapt into the wild breeding population, and subsequently increase the population size of this critically endangered species. However, in May, three juveniles that were captive-reared in 2014 and 2015 were observed, demonstrating the captive-reared mangrove finches are capable of surviving long-term in the wild. These sightings prove the effectiveness of the project, which is great news for all involved.

Francesca Cunninghame©

Francesca Cunninghame©

With this past month marking the release of the third group of captive-reared fledglings since 2014, a total of 36 mangrove finches have now been released into the wild. The team are hopeful that in future years, captive-reared birds may be observed nesting, increasing the population of mangrove finches one bird at a time. Great news for conservation, the Islands, and future generations!

The Mangrove Finch Project is a bi-institutional project carried out by the Charles Darwin Foundation and Galapagos National Park Directorate in collaboration with San Diego Zoo Global and Durrell Wildlife Conservation Trust. The project is supported by Galapagos Conservation Trust, Marguerite Griffith-Jones, GESS Charitable Trust, and Decoroom Limited, The Leona M. and Harry B. Helmsley Charitable Trust, the Swiss Friends of Galapagos, Fondation Ensemble, the Holbeck Trust and several individual donors.

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