The mangrove finch belongs to the group of birds commonly referred to as ‘Darwin’s finches’, and is endemic to the Galapagos Islands. It has highly specific habitat requirements, with breeding populations occurring only in two small areas of pristine mangrove forest on the north-west coast of Isabela. Its extinction across much of its former range makes the mangrove finch one of the most range-restricted birds in the world, with less than 100 individuals remaining.
Adult mangrove finches have dull brown plumage, becoming more olive-toned towards the rump, and whitish, lightly streaked underparts. Males develop black feathers on the head and neck after several annual moults. The beak is long and pointed, and, like many of Darwin’s finches, has evolved for efficient food collection. Mangrove finches use their delicate beaks to lift the scales of tree bark, allowing them to retrieve insect prey from underneath, as well as to probe through the leaf litter.
Breeding occurs in the wet season, generally between December and April. Male finches hold territories which tend to stay constant from year to year, into which they will attract a female who they will often mate with for life. Breeding begins with the male starting to build a nest high up in the canopy, beside which he will sing loudly. The female will help to complete the nest, before laying an average of three eggs, which she incubates for 14 days. During incubation, the male feeds the female at regular intervals. After the chicks hatch, they will remain in the nest for a further 14 days, with both parents delivering food to them. Following fledging, the chicks remain with the male for several weeks, often feeding low down on the ground.
Where to see them: Their range is now restricted to Playa Tortuga Negra and Caleta Black on the north-west coast of Isabela but given the fragile nature of the population, these sites are strictly off-limits for tourists.
When to see them: Mangrove finches are present on the island all year round, but are cryptic and hard to observe outside the breeding season. Adult males sing during the breeding season (December to April), making them more conspicuous.
Threats: Introduced black rats can cause large reductions in breeding success, as they predate both eggs and chicks. Successful control of rats has increased breeding success; however it is still kept extremely low due to parasitism from the larvae of an introduced fly (Philornis downsi) which suck the blood of the nestlings. Over a third of nestlings died from this parasitism in 2013. If a nest fails early on in the breeding season, the parents will nest again in a nearby tree, with nesting attempts later in the season often being more successful.
Conservation actions: The Mangrove Finch Project aims to better our understanding of the biology and ecology of mangrove finches and to minimise the impact of introduced species on their breeding success. The project is also testing the head-starting concept, whereby chicks from early broods are collected and hand-reared before releasing them, giving them a head-start and increasing their chances of survival. The parents then re-nest later in the season, giving them a better chance of successfully raising their own brood. To learn more about this project, visit our Mangrove Finch Project page.