Fighting to save the mangrove finch

Scientists target Invasive Black Fly


Photo credit Kirk Zufelt

Photo credit Kirk Zufelt

SANTA CRUZ, Galapagos, Ecuador — The mangrove finch, a little brown bird that Charles Darwin studied as he developed his theories of evolution, is dangerously close to extinction.  Scientists say there may be fewer than 80 of them left.

The birds have been fending off feral dogs, rats, and fire ants for years. Now they are under attack by the larvae of a black fly, known formally as Philornis downsi.  The larvae get into mangrove finch nests, crawl into the noses and ears of fledgling finches and suck their blood.  Very few of the fledglings survive.

“The fly is in danger of pushing the mangrove finch over the edge,” said Tui de Roy, a wildlife photographer who grew up in the Galapagos and has been photographing the islands for National Geographic and other magazines for decades.

Scientists from the United States and six other countries are working together to combat the black fly.

In the Galapagos, half a dozen experts at the Charles Darwin Research Station on Santa Cruz Island have begun flying out by helicopter to the beach where the mangrove finch nest and collecting fledglings and eggs. They feed the chicks and put the eggs in incubators. When the birds are strong enough, the scientists take them back to the wild.  The scientists are studying the possibility of countering the black flies with wasps and with a sprayed chemical that makes it difficult for them to find each other and mate.  But they worry that their tactics might harm other animals and perhaps plants as well.

“We are exploring what the best options are,” said Jacqueline Rodriguez, an Ecuadorean entomologist at the Darwin Station.

The fly is one of 1,400 plants and animals that have been brought to the islands – both intentionally and accidentally — and are known as invasive species. These plants and animals, scientists say, are the single most serious threat to the Galapagos.  They compete for food and territory with native plants and animals and sometimes, as in the case of the black fly Philornis downsi, they kill Galapagos plants and animals. More than 500 of the invasive species are insects like the black fly. Another insect, the fire ant, kills baby tortoises and birds. The puffy, white cottony cushion scale, a relative of the cicada, sucks the sap of trees and shrubs until they wither and die.

Goats and pigs have been among the most destructive invasive animals. They eat the grass that Giant Galapagos Tortoises need. The wild blackberry from Asia, another invasive species, grows as high as 15 feet and harms other shrubs and trees by blocking their sunlight. The blackberry grows in thick patches that can become impenetrable for migrating tortoises.

One insect, the paper wasp, eats moths, butterflies and caterpillars that are favorites of the mMangrove finch, other finch and wasps that are found only in the Galapagos. Scientists say that few of the endemic wasps have survived.

Scientists at the Charles Darwin Research Station discovered that they could kill paper wasps simply by putting soapy water in a bright yellow bucket.

“Wasps are attracted to the color of the bucket,” said Rodriguez.

The wasps dive into the water to get a drink, she said. But the soap drags them down and they drown.

For several years, scientists from the Darwin Station and the Galapagos National Park have been helicoptering to the dark, volcanic-sand beach on Isabela Island, on the western edge of the Galapagos, where the last of the mangrove finch live.

The scientists are out there for stretches of a month or so living in canvas tents and getting resupplied by boat.  Wearing yellow safety helmets and harnesses around their waists and shoulders, the scientists climb into mangrove trees to find finch nests. They gather chicks and speckled mangrove finch eggs and eventually take them back to the laboratory at the Darwin Station.           The scientists use tweezers to feed the chicks 15 times a day, said Francesca Cunninghame, a New Zealand bird specialist, who is leading the work at the Darwin Station.

The menu for the chicks is made up of wasp larva, papaya pellets, ground chicken, scrambled eggs and moths.

After about six weeks, the scientists go back into the field with the young chicks. They stay with them for about a month to make sure they are adjusting.

It is not clear when counter measures for the black fly will be developed, but Cunninghame and the others say they can’t wait.  “We need to get in first and start doing something to boost the mangrove finch population until we find a way to control the fly,” Cunninghame said.

The scientists returned the first of the laboratory-raised finch to the island of Isabela in 2014 – 13 birds.  The next year it was eight and in 2016 they put 16 birds back in their home territory.

Raising mangrove finch is slow work and it is hard to say where things are heading, said Gunter Reck, a former head of the Darwin Station and the founding dean of the School of Environmental Science at the University of San Francisco in Quito.

“They are in such small numbers anything could happen,” Reck said.

fly 2


More like this: Galapagos 2016

Back to Top