Mangrove Finches Revitalized in Galapagos

First Fledged Mangrove Finch
Charles Darwin Research Foundation Photo 

It’s wonderful to be able to share another great success for saving an endemic Galapagos species. The Charles Darwin Foundation (all photos attributed to the foundation) has raised eight endangered mangrove finches and released them onto Isabela Island.0


I can remember growing up with mangrove finches in my garden and seeing them on just about every cruise trip. But that once frequent event has changed and, for years, a finch sighting has been rare, if indeed we see one at all. That these important symbols of evolution are, with help from scientists, reviving, is a monumental step toward rejuvenation of the species.

Galapagos Foundation Photo

Of all the Darwin finches, the mangrove finch is the rarest. Its population is estimated to be less than 100 individuals. Within these individuals, there are only 20 breeding pairs. And, equally significant is that even when the finches mate successfully, the mortality rate of the hatchlings has been a staggeringly high 95% because of the invasion of a parasitic fly. I wrote about this fly in a previous post.

In February, scientists collected eggs from mangrove finch nests on Playa Tortuga Negra and incubated them as though they were in the wild. When they hatched, the little fledglings were hand-reared until they were ready for independence. 

But, they didn’t go directly from their Santa Cruz baby nursery to the wild. Rather, they were placed

Released Finch in the Wild, Foraging for Food
Galapagos Foundation Photo

in what is called a pre-release aviary located inside the mangrove forest for three weeks. There, they were able to start the adaptive process and get to know the environment of their soon-to-be home. During this period, they were fed natural food eaten by the mangrove finch.

After three weeks, it was time for the experiment to continue. Tiny transmitters were placed at the base of the birds’ tail feathers to allow for monitoring. In addition, colored rings were placed on their legs for easy identification. The aviary was opened and the finches were allowed to come and go as they wished. Birds who returned found food waiting for them. Monitoring took place and at the beginning most returned. Eventually fewer returned as they adapted to the wild. Monitoring indicates that most of the juveniles stayed at Playa Tortuga Negra, but some went north and other south toward Darwin Volcano and Tagus Cove.

Monitoring Released Finches
Galapagos Foundation Photo

As for the success of the mangrove finch release program, Francesca Cunningham, project leader for the Mangrove Finch Captive Rearing Program, had this to say:

“Releasing and monitoring eight mangrove finches bred in captivity, as they adapt to their natural habitat, is incredibly rewarding. Unfortunately, 2015 was a much more challenging year compared withour first attempt in 2014 and we have released fewer finches than hoped. However, eight young birds, released back into the wild once safe from the threat of P. downsi is a significant boost to the juvenile population, and from previous research we know that none of them would have survived as chicks in the wild.”

Finch Photo from New Scientist

Unfortunately, the parasite has not been eradicated yet, so those finches born in the wild still suffer from the high mortality rate. Still, steps are being taken to see that this unique and important species, while endangered, does not become extinct.

Baby Mangrove Finch
Photo from Galapagos Conservancy

In fact, in August 2015, the journal New Scientist revealed that during field work in Galapagos, Sabine Tebbich of the University of Austria in Vienna observed that four difference species of Darwin finch were picking leaves from a Galapagos guava tree and rubbing those leaves on their feathers. Further study disclosed that the sap from the leaves repels invasive mosquitos and, by so doing, inhibit the growth of the "bloodthirsty parasitic larvae" that are threatening the baby finches. These findings were presented at the Behaviour meeting in Cairns, Australia, but remain tentative until further study and formal publication. To learn more, go to New Scientist.