First release of critically endangered mangrove finches into Galapagos forest

Biologists from the Charles Darwin Foundation, Galapagos National Park Directorate, and San Diego Zoo Global are celebrating the release of 15 mangrove finches into the mangrove forest habitat on the island of Isabela, Galapagos, Ecuador. This is the first time these critically endangered birds have been captive reared and released into the wild. The release of these birds is part of a new initiative designed to increase the wild population of the species.

"The mangrove finch is the most threatened bird species in the Galápagos, with an estimated population of only 80 birds," said Francesca Cunninghame, lead scientist for the Charles Darwin Foundation. "This first season of the program has been a great success and we have increased mangrove finch fledging success by over 200%."

In February, mangrove finch eggs and newly hatched chicks were collected from wild nests at Playa Tortuga Negra. The eggs and chicks were transferred to the Charles Darwin Research Station, Santa Cruz, for artificial incubation and hand-rearing. During March, the fledglings were transported back to Playa Tortuga Negra, where they were placed in pre-release aviaries to allow them to adapt to their natural environment. After four to six weeks in the aviaries, the first group of seven birds was released on April 20. This was followed by subsequent releases until all 15 of the chicks raised in captivity were freely exploring their wild habitat. "Until now, mangrove finch nestlings had a very high rate of mortality due to an introduced parasitic fly, Philornis downsi," said Richard Switzer, associate director for San Diego Zoo Global. "By headstarting' the youngsters through captive propagation, we have been able to protect this year's hatchlings and improve the species' chances for conservation."

Going from captivity to the forest represented a big transition for the young finches. Time spent in the pre-release aviaries, monitored by conservationists, gave the young birds an opportunity to adapt to life in the wild. During this transition the mangrove finches were given a captive diet and also encouraged to search for naturally occurring food among the dead logs, leaf litter, tree branches, native fruits and black mangrove seeds in the aviaries.

"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 the Philornis can be controlled," said Beau Parks, a senior keeper on the San Diego Zoo team. "As zoo biologists, it is rewarding to see finches, which we had collected as eggs and then hand-reared, returning back to their forest habitat to boost the wild population."

Before releasing the finches, tiny transmitters weighing 0.3 grams were attached to each bird, allowing the field team to monitor the bird's survival and dispersal for up to 22 days. During this time, fledglings were observed foraging, interacting with their wild counterparts and dispersing over neighboring lava fields. Additionally, the aviaries remained open for several weeks after release 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.

"In order to reach our objectives the Environmental Authority always needs the collaboration of strategic allies who provide us with technical and scientific assistance," Said Arturo Izurieta, Director of the Galapagos National Park Directorate.