Chicks fledge against all odds for the rarest bird in Galapagos - Season 2019

A mangrove finch fledgling a short time after leaving its nest

The Charles Darwin Foundation (CDF) and Galapagos National Park Directorate (GNPD) team are back from two months of fieldwork in a remote part of Isabela Island, a small patch of mangrove forest nestled between harsh lava fields reached by a six hour boat ride from Santa Cruz Island. This is the only place where the rarest bird in Galapagos, the mangrove finch, is found in the world.

Playa Tortuga Negra where the Mangrove Finch is found
Playa Tortuga Negra where the Mangrove Finch is found
Mangrove forest at Playa Tortuga Negra where the Mangrove Finch is found
Mangrove forest at Playa Tortuga Negra where the Mangrove Finch is found. Photo by: Juan Manuel García, CDF.

The team found only 10 breeding pairs this year, down from 12 the previous year. With intensive monitoring and management of the nests located high up in the top of thin black mangrove trees they were able to ensure successful fledgling of five chicks.

Francesca Cunninghame,Jorge Jimenez and GNPD ranger Roberto Ballesteros looking for a mangrove finch nest
Francesca Cunninghame, Jorge Jimenez and GNPD ranger Roberto Ballesteros looking for a mangrove finch nest. Photo by: Juan Manuel García, CDF.
Jorge Jimenez climbs up black mangroves in order to protect mangrove finch nestlings from parasitism from the introduced fly larvae P. downsi. This intensive management in the field enables the team to protect the nestlings in their natural habitat
Jorge Jimenez climbs up black mangroves in order to protect mangrove finch nestlings from parasitism from the introduced fly larvae P. downsi. This intensive management in the field enables the team to protect the nestlings in their natural habitat. Photo by: Juan Manuel García, CDF.

The species is threatened by introduced rats which eat the birds’ eggs, and an invasive parasitic fly (Philornis downsi) that sucks the blood of the chicks. Conservation management is carried out throughout the year to keep the rat population under control, and during the breeding season intensive management of every nest is conducted to reduce the number of fly larvae attacking the chicks.
A Philornis downsi larvae taken out of a nestling’s nostril.

Philornis downsi larvae removed from an abandoned mangrove finch nest. Without thorough treatment of the nests these parasites cause extremely high nestling mortality
Philornis downsi larvae removed from an abandoned mangrove finch nest. Without thorough treatment of the nests these parasites cause extremely high nestling mortality. Photo by: Juan Manuel García, CDF.
Invasive black rat population control
Invasive black rat population control. Photo by: Juan Manuel García, CDF.

To protect the chicks, a natural pesticide needs to be carefully injected in to the base of the nest and some chicks require supplementary feeding.

Injection of a natural pesticide on the base of the nest to reduce the number of Philornis downsi parasites
Injection of a natural pesticide on the base of the nest to reduce the number of Philornis downsi parasites. Photo by: Juan Manuel García, CDF.

The team had hoped for more breeding pairs than in 2018, however dry climatic conditions resulted in only a few females laying eggs. Furthermore four nests were lost due to unprecedented strong winds. Project leader Francesca Cunninghame says:

“Although we had high hopes for this breeding season many pressures worked against the mangrove finches. However to have enabled five chicks to fledge in the wild is a real boost. These five fledglings represent an important addition to the limited population of an estimated 100 individuals.”

However, this year the team observed another problem – most of the black mangroves trees were sick or dying. These trees provide nesting sites for the birds, and the seeds provide caterpillars which are an important food source for the females to enter into breeding condition. Further research is urgently needed to understand what triggered the die back, but it appears that the trees, likely under stress from climate fluctuations, are being affected by a wood boring beetle.

Black mangrove tree affected by a wood boring beetle
Black mangrove tree affected by a wood boring beetle. Photo by: Juan Manuel García, CDF.

On a positive note, this season several young males were observed establishing territories and one young female that had been hand reared raised chicks– to see these individuals forming part of the breeding population demonstrates that the intensive conservation management is helping to stop further declines. CDF and the GNPD are committed to continue to work towards conserving one of the world’s rarest birds from extinction in the face of known and new emerging threats.

Adult mangrove finch foraging for food in the mangrove forest
Adult mangrove finch, that was bred in captivity in 2016, foraging for food in the mangrove forest. Photo by: Juan Manuel García, CDF.
Adult mangrove finch feeding its nestling
Adult mangrove finch feeding its nestling. Photo by: Juan Manuel García, CDF.
Mangrove finch nestling with its distinctive colour rings
Mangrove finch nestling with its distinctive colour rings. Photo by: Juan Manuel García, CDF.

The Mangrove Finch Project is a bi institutional project of the Charles Darwin Foundation and the Galapagos National Park Directorate in collaboration with San Diego Zoo Global and Durrell Wildlife Conservation Trust. The project is funded by Galapagos Conservation Trust, The Leona M. and Harry B. Helmsley Charitable Trust via the International Community Foundation and Friends of Galapagos Switzerland.

A fledgling mangrove finch identified by its colour bands five weeks after leaving the nest. This individual was infested with Philornis larvae as a nestling and the interventions from the field team enabled it to survive and fledge in the wild
A fledgling mangrove finch identified by its colour bands five weeks after leaving the nest. This individual was infested with Philornis larvae as a nestling and the interventions from the field team enabled it to survive and fledge in the wild. Photo by: Juan Manuel García, CDF.

The “Charles Darwin Foundation for the Galapagos Islands”, in French “Fondation Charles Darwin pour les îles Galapagos”, Association International sans but lucratif (“AISBL”), has its registered office located at Chaussée de la Hulpe 177 Bte 20 (rez) - 1170, Brussels, and is registered under the trade registry of Brussels under the number 0409.359.103.

© 2019 Charles Darwin Foundation. All rights reserved.