Fortunes improve for the most threatened bird species in the Galápagos

Biologists have new hope for Mangrove Finch, the most threatened bird species in the Galápagos Islands, following the release in spring 2014 of 15 captive-reared chicks.

It was the first time the Critically Endangered species had been bred in captivity and released into the wild.

The finch’s population numbers only 60 to 80 birds. The entire population is restricted to less than 74 acres in two patches of mangrove forest on the west coast of Isabela Island, the largest island of the Galápagos.

“This first season of the program has been a great success,” says Francesca Cunninghame, lead scientist for the Charles Darwin Foundation, the archipelago’s oldest private scientific research organization. “We have increased Mangrove Finch fledging success by over 200 percent.”

The foundation coordinated the project with the Galápagos National Park Directorate and San Diego Zoo Global. Funding came from SOS – Save Our Species, the International Community Foundation, Durrell Wildlife Conservation Trust, and Galápagos Conservancy.

In February, finch eggs and newly hatched chicks were collected from wild nests in mangrove forest on Isabella and transferred to the Charles Darwin Research Station on Santa Cruz Island for artificial incubation and hand-rearing. In March, the fledglings were transported back to Isabella, 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. By early May, all 15 of the chicks raised in captivity were released and exploring their wild habitat.

“Until now, Mangrove Finch nestlings had a very high rate of mortality due to an introduced parasitic fly, Philornis downsi,” says Richard Switzer, associate director for San Diego Zoo Global. “By head-starting the youngsters through captive propagation, we have been able to protect this year’s hatchlings and improve the species’ chances for conservation.”

The Philornis fly lays its eggs in the nests of finches. Its larvae then parasitize nestlings. The fly is largely responsible for a high mortality rate in the Mangrove Finch in recent years.

“We are very encouraged by what we were able to accomplish with the finch this year and are hopeful that the hand-rearing program can help the species survive until the Philornis can be controlled,” says Beau Parks, a senior keeper from San Diego Zoo Global. “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.”

Tiny transmitters weighing 0.3 grams were attached to each bird before release, allowing the field team to monitor 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. The aviaries remained open for several weeks after release, and the team maintained a continuous presence to observe birds that returned for supplementary food. As the birds became more independent, the frequency of their visits decreased. — Matt Mendenhall, Managing Editor

Originally Published June 10, 2014