Mangrove Finches: from captivity back to their natural habitat

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Captive reared mangrove finch fledgling at the moment of its release (Photo courtesy of F. Cunninghame, CDF).

The Charles Darwin Foundation (CDF), the Ecuadorian Ministry of Environment through the Galapagos National Park Directorate (GNPD) and San Diego Zoo Global (SDZG) are celebrating the release of fifteen Mangrove Finches into the forest habitat on Isabela Island, Galapagos, Ecuador.

This is the first time these critically endangered birds have been captive reared and released into the wild as part of a new conservation initiative aimed at increasing the wild population so as to safeguard the future of this species.

Francesca Cunninghame, the CDF scientist leading the project, has just returned from Playa Tortuga Negra one of the two small mangrove forests which the finches inhabit. These forests, comprising just 30 ha (75 acres), represent the entire remaining range of the species.

Francesca explained the significance of this reintroduction effort:

“The Mangrove Finch is the most threatened bird species in the Galapagos with an estimated population of only 80 individuals.

Based on the results of our post-release monitoring activities, we can conclude that this first season of the program has been a great success and more so if we consider that this year only six chicks fledged in the wild. This season alone we increased mangrove finch fledging success by over 200%.

We now have a way to significantly increase the number of fledglings produced each year while methods are developed to control their main threat, the introduced parasitic fly Philornis downsi which causes a very high rate of mortality in nestlings.

This important step for the conservation of the mangrove finch is the result of strong team work from all project partners and collaborators.”

Lorena Tapia, Ministry of Environment stated:” The Ministry of Environment has focused most of its efforts in restoring populations that have been seriously threatened, as is the case of the Mangrove Finch. We are very proud of the results achieved and we are sure that this is a great step towards the recuperation of this species.”

Arturo Izurieta, Director of the GNPD said: “In order to reach our objectives the Environmental Authority always needs the collaboration of strategic allies who provide us with technical and scientific assistance.” 

During February this year, these finches were collected as eggs or newly-hatched chicks from wild nests at Playa Tortuga Negra. The eggs and chicks were transferred to the Charles Darwin Research Station, on Santa Cruz Island, for artificial incubation and hand-rearing.

Once the chicks had learned to feed independently, at approximately 4 weeks old, they were ready to return to their natural habitat. By mid March, the fledglings, together with a team of researchers and park rangers, returned back to their forest where purpose built pre-release aviaries waited for them amidst the mangroves.

Going from captivity to the forest represented a big transition for the young finches. The pre-release aviaries allowed them to adapt to their natural environment. Although a captive diet was still provided for the birds, the aviaries were filled with dead logs, leaf litter, tree branches, native fruits and black mangrove seeds containing caterpillars to encourage them to search for natural food.

On 20th April, after four to six weeks since their arrival back to their habitat, the aviary doors were opened for the first time, releasing the seven oldest birds. This was followed by two subsequent releases up until May 6th when all 15 chicks raised in captivity were freely exploring their wild habitat.

Before releasing the finches, tiny transmitters weighing 0.3 grams were attached to each bird, which allowed the field team to monitor their survival and dispersal for up to 22 days.

After their release, the fledglings were observed foraging, interacting with their wild counterparts and dispersing over neighboring lava fields. Additionally, the aviaries remained open for several weeks  and the team maintained a continuous presence observing birds that returned for supplementary food. As the birds became more independent, the frequency of their visits decreased. 

The field team was still able to locate eight of the 15 chicks up until the time of their departure on the 16th of May. Seven chicks were in the mangrove forest at Playa Tortuga Negra and one was in a patch of mangroves to the north. Although the team lost track of seven finches, evidence suggests that these birds had dispersed out of the immediate mangrove forest habitat, and no mortalities were confirmed.

Beau Parks, a member of the SDZ team, added: "We are very encouraged by what we were able to accomplish with the Mangrove Finch this year and are hopeful that the hand-rearing program can help the species survive until Philornis can be controlled. As zoo biologists, it was wonderfully rewarding to see the finches, which we had collected as eggs and then hand-reared, returning back to their forest habitat to boost the wild population."

The Mangrove Finch project is a bi-institutional initiative between the CDF and the Ecuadorian Ministry of Environment through the GNPD and in collaboration with SDZG. It is funded by SOS - Save Our Species, the International Community Foundation (with a grant awarded by The Leona M. and Harry B. Helmsley Charitable Trust), Durrell Wildlife Conservation Trust and Galapagos Conservancy. Several private individuals have also contributed with financial and in-kind support.