Conservationists are excited that the critically endangered Galápagos mangrove finch has had its most successful breeding season on record.
In the 2026 breeding season (December to April), researchers recorded 20 breeding pairs and 25 successful fledgelings.
Although this doesn’t sound like many, it’s a huge boost compared to the 2025 season which had 11 breeding pairs and just eight successful fledglings.
“For the first time in many years, we are seeing sustained reproductive success at a scale that gives us more realistic hope for the future of the mangrove finch,” says María Igual Beltrán, principal investigator of the Mangrove Finch Project at the Charles Darwin Foundation.
“These results suggest that long-term conservation actions and improvements to our management strategies are making a measurable difference for one of the most endangered birds on Earth.”
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The Galápagos mangrove finch (Camarhynchus heliobates) has had a rough ride. The species was almost wiped out by the terrifyingly named avian vampire fly (Philornis downsi). This invasive, parasitic fly lays its eggs in birds nests and, when the larvae hatch, they drink the blood of the baby birds, often killing them.
To try to protect them before they became extinct, Charles Darwin Foundation researchers worked with rangers from the Galápagos National Park Directorate on a conservation method called the 'self-fumigation' technique.
They offered the birds cotton and plant fibres treated with an insecticide called Permacap to use in nest-building. This pesticide prevents the flies from invading the nest without harming the birds.
The method wasn’t an immediate success but, through trial and error, the scientists found the best way to encourage the birds to accept the protective materials and use them to build nests.
“Not all bird species respond to materials in the same way, and it took years for us to understand how mangrove finches preferred to ‘receive’ the treated fibres,” says Igual Beltrán. “We discovered that placing the fibres tied to branches early on in the breeding season worked remarkably well – the birds consistently collected them there.”
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Self-fumigation trials began in 2017 but it wasn’t until 2023 that the experts hit on the winning strategy. They also found that some types of material worked better than others. “Cotton and sisal fibres proved especially effective,” she adds. “Every nest we analysed after fledglings had left contained treated material and showed no presence of the blood sucking fly larvae.”
The success of this year’s breeding season gives conservation teams hope that this intervention is really working. Providing pesticide-treated nest materials “was undoubtedly one of the key reasons behind this season’s successful results,” says Igual Beltrán.
The recovery offers hope for the future of this rare species of Darwin’s finch which is endemic to the Galápagos and is only found in two small patches of mangroves on Isabela Island.
Despite a promising season, the battle to save the species is not yet won. “These results do not mean the species is out of danger,” says Rakan Zahawi, executive director of the Charles Darwin Foundation, “but they do represent one of the most encouraging advances in decades of conservation work in support of this species in Galápagos.”
Top image: Galápagos mangrove finch. Credit: Charles Darwin Foundation
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