Earlier in 2014, sixteen tiny eggs were collected from two small pockets of mangrove forest on the western side of Isabela in the Galapagos Archipelago. These eggs, each the size of the nail on your little finger, belong to one of the rarest and most range restricted birds in the world: the mangrove finch (Camarhynchus heliobates). This small, brown, unassuming bird is one of the famous Darwin’s finches and is today the rarest endemic bird in Galapagos. There are less than 100 mangrove finches alive today and last year there were only 14 breeding pairs. But why are they so critically endangered?
Until recently, one of the main threats to mangrove finches was introduced rats. As generalist carnivores, rats would seek out and feed on the eggs and chicks of finches during the breeding season. Fortunately, rats are now being controlled at the breeding sites but now a much smaller invasive species poses an even larger threat.
Philornis downsi is a species of fly native to Trinidad and Brazil. It was introduced to Galapagos in the 1960s and has now spread to 14 islands within the Archipelago. The adults of this fly are harmless, feeding almost exclusively on nectar, but in their larval stage they are blood-sucking parasites. Female flies lay their eggs in the nests of small breeding land birds. Blind, naked and weak, the mangrove finch hatchlings are an easy target for the fly larvae which feed on their blood, very often resulting in the death of the chick. In 2013, 37% of chicks were killed this way – a massive hit to such a tiny population.
So why are the scientists removing eggs? In an effort to ensure that the mangrove finch does not become the first bird to go extinct in Galapagos since before Darwin’s time, scientists from the Charles Darwin Foundation and San Diego Zoo are, with support from the Galapagos National Park, taking action. During the mangrove finch breeding season, females lay up to five clutches of eggs but the first few rarely survive. By taking this first clutch, hatching and raising the chicks in captivity, then releasing them back into the wild when they are old enough, the project should result in more individuals being added to the population each year.
By raising the chicks in captivity, they will have avoided the nest-bound parasites and will have been given a ‘head-start’ in life. 2014 was the first time ‘head-starting’ has been trialled on mangrove finches and it is proving a great success. The sixteen eggs have hatched and the mangrove finch chicks are being released back into the mangroves right now. The future of the mangrove finch is starting to look a little brighter.
For more information on the project and to keep up to date with progress, please visit www.mangrovefinchappeal.org