Giving the Mangrove Finch a Head-start to Recovery

An adult Mangrove Finch in the wild – the most geographically restricted songbird in the world. Photo courtesy of the Charles Darwin Foundation.

An adult mangrove finch in the wild, the most geographically restricted songbird in the world. Photo courtesy of  Charles Darwin Foundation

I arrived on the rugged and spectacular island of Santa Cruz, in the Galápagos islands, in the middle of January. This was my second trip to Galápagos within the space of three months. The first had been in October 2013, when I joined forces with Francesca (Franny) Cunninghame, the team leader of the Charles Darwin Foundation’s mangrove finch project, on a reconnaissance mission to investigate the possibility of San Diego Zoo Global collaborating with the Foundation and Galápagos National Park on an exciting new initiative to prevent the extinction of the mangrove finch Camarhynchus heliobates and, hopefully, start the species on the path to recovery.

The mangrove finch is one of 13 closely related finch species found throughout Galápagos, named in honor of Charles Darwin, following his now legendary studies in Galápagos and his resulting theories on evolution by natural selection. All the species of Darwin’s finches superficially appear fairly similar: small, brown, sparrow-like birds (although actually more closely related to tanagers), with bold and naïve behavior around humans. What distinguishes the different species is the diversity of beak morphology, which varies according to their feeding habits and the ecological niches to which they have adapted. These beak shapes range from the large, sturdy beaks of the seed eaters to the thin, pointed beaks of the insectivores (like the mangrove finch), which probe around in bark and leaves in search of invertebrates.

Currently, the most crucial distinction of the mangrove finch is its status as a critically endangered species. It is the most threatened bird in Galápagos, with only 60 to 80 individuals remaining. The species is now restricted to two tiny patches of mangrove forest on the west coast of the island of Isabela. The entire population has a tiny range of less than 75 acres, which equates to the size of one of the field exhibits at the San Diego Zoo Safari Park! In the past 10 years, populations on the east coast of Isabela and another island, Fernandina, have become extinct. The mangrove finch’s adaptation to its mangrove habitat, which is sporadically dotted around the volcanic coastline, probably predisposed it to being one of the less abundant species of Darwin’s finches. But with the human-caused threats to its existence, the mangrove is hanging on by a fragile thread.

Philornis larvae in a finch nest. Photo by J. O’Connor; courtesy of the Charles Darwin Foundation.

Philornis larvae are found in a finch nest. Photo by J. O’Connor; courtesy of Charles Darwin Foundation.

Like other island ecosystems throughout the world, Galápagos is beginning to suffer the impacts of humans and the threats they bring. Threats to the mangrove finch include introduced rats, cats, disease, and possibly the nonnative cuckoos called smooth-billed anis. For many of the land birds, public enemy number one is an inconspicuous and harmless-looking fly, known as Philornis downsi, which is a species of botfly that lays its eggs in the nests of the finches. When the Philornis larvae hatch, they engage in activities that are certainly less benign than their parents, infesting the nostrils and ears of the chicks, and then sucking the blood from the body and eventually killing them. As a result, only a very small percentage of mangrove finch chicks make it to fledge, so the species is at risk of simply disappearing due to lack of recruitment. Additionally, the mangrove finch’s tiny population increases the chance of suffering from inbreeding depression, and being located in only one small location, the species is also at particular risk from natural disasters (such as lava flows, fire, or disease).

This all helps to explain my return to Galápagos in January to embark on an exciting new pilot project with our Galápagos partners. Our goal is to implement a “head-starting” program to help mangrove finch chicks through the vulnerable nestling phase while under threat from Philornis. The first step is to collect eggs (and possibly newly hatched chicks) from wild nests and transport them to the island of Santa Cruz. The second step is to hatch the eggs and hand-rear the chicks. If these first two steps are successful, we hope to return the young birds back to the mangrove on Isabela, where they will be cared for in a purpose-built acclimation aviary before being released back into the mangrove forest and monitored by the field team. The real measure of success will be the survival of these youngsters back in their mangrove habitat. Ultimately, we hope to keep the mangrove finch afloat as a species and perhaps even re-establish recently extinct populations, while the Charles Darwin Foundation and its partners find a solution to the devastation caused by Philornis. More information on its work with Philornis can be found here.

We are very fortunate that the San Diego Zoo’s Avian Propagation Center (APC) is one of the world leaders in the incubation and hand-rearing of a range of bird species, from hummingbirds to harpy eagles. Similarly, the Hawaii Endangered Bird Conservation Program of our Institute for Conservation Research specializes in the artificial propagation of critically endangered birds, of which the Hawaiian honeycreepers are not too dissimilar from the Darwin’s finches. Our collaboration represents an exciting opportunity to apply these techniques as a vital conservation tool for the mangrove finch.

The new Mangrove Finch egg and chick room takes shape, ready to receive the first eggs. Photo by Beau Parks / SDZG.

The new mangrove finch egg and chick room takes shape, ready to receive the first eggs.

Months of planning have gone into our endeavor. Much of the specialist resources, such as incubators, brooders, and veterinary equipment, are not available in Galápagos. So we had to pack all the gear, carefully thinking through the whole process, from harvest of wild eggs to the release of young birds. Equally crucially, we had to plan what food items and nutritional supplements we would be feeding the chicks, knowing that many of the usual chick-rearing food items, such as waxmoth larvae and crickets, would not be readily available. Finally, we had to plan for “what if…?” scenarios, such as back-up electrical supplies in case of power cuts.

Pre-release aviaries were constructed on one of the few patches of dry land within the heart of the mangrove forest. Photo by Francesca Cunninghame / Charles Darwin Foundation.

Pre-release aviaries were constructed on one of the few patches of dry land within the heart of the mangrove forest. Photo by Francesca Cunninghame, Charles Darwin Foundation.

Upon my arrival in Galápagos with four large action packers of equipment, I teamed up with Anita Carrion and other staff to create an artificial propagation facility from an unused room at the Charles Darwin Research Station. My first weekend was spent up a step-ladder, painting the walls of our new egg and chick room, as well as disinfecting every surface. So much for the glamorous life of a conservation biologist in Galápagos! Working in Galápagos comes with a unique set of challenges, including the availability of many simple items we might otherwise take for granted. For example, it took the best part of two days to locate and purchase tables suitable for our incubation and hand-rearing activities. One of our biggest concerns is that many of the other wild finches around Puerto Ayora are infected with avian pox; the lesions are evident on their toes and faces. It is critical that the mangrove finch chicks should be raised in disease-free conditions, so there is minimal risk of them transmitting pox back to the eventual release site in the mangrove. Consequently, our egg and chick room was installed with an air-lock vestibule, which includes a fly-zapper to prevent the entry of mosquitoes. Finally, Franny and a team of contractors had already constructed release aviaries in the heart of the mangrove forest, within the last remaining core habitat of the mangrove finch, in hopeful expectation of our success.

By the time the egg and chick room was ready for approval for the Galápagos biosecurity agency, Franny and her field team were already camped out on the beach that neighbors the mangrove forest on Isabela, known as Playa Tortuga Negra. There, they began searching for nests, monitoring for incubation behavior, and erecting a complex rigging of ropes, which would subsequently be used to access the wild nests to collect the eggs. Then, our own Beau Parks arrived with two more large boxes of equipment to put the finishing touches to the egg and chick room. Anxiously we awaited news of the nests at Playa Tortuga Negra (via a temperamental satellite phone) so that we could make the necessary arrangements for the  nerve-wracking procedure of collecting the eggs, transporting them more than 100 miles between islands (while ensuring that the embryos remained alive and healthy), and starting the process of artificial propagation.

Richard Switzer is an associate director of applied animal ecology at the San Diego Zoo Institute for Conservation Research.

One Response to Giving the Mangrove Finch a Head-start to Recovery

  1. This is an amazing Blog about darwin’s Finch!!! I really enjoyed reading it! :)