Biology
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The mangrove finch mainly feeds upon adult insects, grubs and spiders, which are obtained by foraging through the leaf litter, or by using its powerful beak to prise off bark from dead wood. As an alternative, particularly when food is scarce, this species employs a more ingenious method of feeding. Like the woodpecker finch (Camarhynchus pallidus), this species is known to use cactus spines and twigs to prise out inaccessible grubs from tree hollows and cavities (2).
The mangrove finch normally breeds throughout the hot, wet season, commencing in December or January and lasting until May (5). Darwin's finches usually form monogamous, lifelong breeding pairs, although mate changes and breeding with more than one partner have also been observed. Generally a clutch of three eggs is laid, which are incubated by the female for about twelve days, and the young brooded for a further two weeks before leaving the nest (3).
Conservation
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For over a decade, the Charles Darwin Foundation (CDF) has been working to conserve the mangrove finch (2). At present, extensive research is being conducted to better understand this species' breeding biology and to determine the causes of its decline (2) (5). In the meantime, active protection of the remaining breeding populations is being employed through predator and nest parasite control (5). Despite these measures, the mangrove finch remains extremely vulnerable due to its limited range. In order to address this, the CDF and the Durrell Wildlife Conservation Trust are currently working together towards a captive breeding and translocation programme. If successful, their efforts will help to ensure a future for this remarkable species (5) (7).
Description
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Poised on the brink of extinction, the diminutive mangrove finch is not only the most endangered of Darwin's finches, but is also one of the rarest birds worldwide (3) (4). Like the other twelve species of Darwin's finches endemic to the Galapagos Islands, this species has evolved a specialised beak shape, enabling it to exploit a particular habitat and diet (3). In the case of the mangrove finch, the beak is long and pointed, with a down-curved culmen, enabling this species to lift scales of tree bark, and pick off insect prey (2). Plumage is dull brownish above, becoming olive on the rump, while the underparts are whitish with faint streaking (2) (5). Males can be distinguished by the black colouration that develops on the head and neck over the course of several annual moults (5) (6).
Habitat
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The mangrove finch has highly specific habitat requirements, and will only occupy dense mangrove swamps that are separated from the sea, where a large amount of leaf litter and dead wood is able to accumulate, instead of being carried away by currents (5).
Range
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Historically, the mangrove finch was known to occupy at least six mangrove patches on the islands of Fernandina and Isabela in the Galapagos Archipelago. Today, however, this species is extinct on Fernandina, and breeding populations are only recorded at two locations on the north-west coast of Isabela (5).
Status
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Classified as Critically Endangered (CR) on the IUCN Red List (1).
Threats
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With a declining population of less than 100 adult birds (3) and a breeding range of around one square kilometre (5), the mangrove finch's situation is critical. The exact cause of this species' decline is unclear, but, natural factors such as the El Niño cycle, introduced species, and human activities may all be involved (2). As a result of introduced predators such as black rats, cats and the smooth-billed ani preying on eggs and chicks, and high levels of nest infestation by the blood sucking parasite, Philornis downsi, causing the death of nestlings, the mangrove finch's breeding success is low (2). Concerted conservation action is necessary if this species is to be saved from extinction.
Mangrove finch
provided by wikipedia EN
The mangrove finch (Camarhynchus heliobates) is a species of bird in the Darwin's finch group of the tanager family Thraupidae. It is endemic to the Galápagos Islands. It was found on the islands of Fernandina and Isabela, but recent surveys have failed to record the species on Fernandina. It has been classified as critically endangered by BirdLife International, with an estimated population of 20–40 mature individuals in 2021, located in two large mangroves on Isabela.[1] A study has shown that the two small populations remaining on Isabela Island have begun undergoing speciation and that one or both populations will eventually become extinct due to a lack of interbreeding.[2]
Habitat
As its name suggests, the mangrove finch lives in the mangroves of the Galápagos Islands. The mangrove finch feeds upon the various insects, larvae, spiders, and vegetable matter found in the mangroves. It closely resembles the far commoner woodpecker finch, but is not known to use tools.
Predators
The main predators of the mangrove finch are cats, fire ants, paper wasps, and especially destructive black rats and parasitic flies. The black rats (Rattus rattus) are predators that account for 54% mortality rate of the mangrove finch during egg incubation, while the larvae of the avian vampire fly (Philornis downsi) add an additional 14% mortality rate of newly hatched chicks.[3] Due to high predation rates in 2007 and 2008, rat poison was spread throughout different mangrove sites where the finches lived, which decreased rat predation to 30% mortality of the finch eggs. A year before the rat poison was dispersed, predation was observed in 70% of nests and the average success of nesting was 18%.[4] By 2013, the avian vampire fly (introduced to the Galapagos Islands circa 1960s) had spread and killed about 55% of Darwin's finch nestlings within nests.[5]
Conservation
The mangrove finch is classified as critically endangered on the IUCN Red List, with only 20–40 mature individuals as of 2021.[1]
In January 2014, project researchers reported successfully raising 15 mangrove finch chicks in captivity and releasing them back into the wild. Since then, 36 fledglings have been "head-started" and the project is building on this success.[6]
The Mangrove Finch Project is a bi-institutional project carried out by the Charles Darwin Foundation and Galapagos National Park in collaboration with San Diego Zoo Global and Durrell Wildlife Conservation Trust. The project is supported by the Galapagos Conservation Trust, the Mohamed bin Zayed Species Conservation Fund, Durrell Wildlife Conservation Trust, The Leona M. and Harry B. Helmsley Charitable Trust, Galapagos Conservancy, and the British Embassy in Ecuador.[7]
References
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^ a b c BirdLife International (2016). "Geospiza heliobates". IUCN Red List of Threatened Species. 2016: e.T22723786A94832935. doi:10.2305/IUCN.UK.2016-3.RLTS.T22723786A94832935.en.
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^ "Darwin's rarest finch meets an 'evolutionary dead end'". Ars Technica. 27 June 2010.
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^ Fessl, B, & Young, G (2010). How to save the Rarest Darwin's Finch from Extinction: The Mangrove Finch on Isabela Island. Philosophical Transactions of the Royal Society B: Biological Sciences, 365, 104
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^ Bergstrom, C, & Dugatkin, L (2012). Parasite Infestation and Predation in Darwin's Small Ground Finch: Contrasting Two Elevational Habitats between Islands. Journal of Tropical Ecology, 26, 285.
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^ Kleindorfer, Sonia; Dudaniec, Rachael Y. (2016-08-23). "Host-parasite ecology, behavior and genetics: a review of the introduced fly parasite Philornis downsi and its Darwin's finch hosts". BMC Zoology. 1 (1): 1. doi:10.1186/s40850-016-0003-9. ISSN 2056-3132.
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^ "Mangrove finch chicks born in captivity successfully released". Galapagos Conservancy, Inc. Retrieved 2020-07-06.
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^ "Saving the mangrove finch". Galapagos Conservation Trust. Retrieved 2020-07-06.
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Mangrove finch: Brief Summary
provided by wikipedia EN
The mangrove finch (Camarhynchus heliobates) is a species of bird in the Darwin's finch group of the tanager family Thraupidae. It is endemic to the Galápagos Islands. It was found on the islands of Fernandina and Isabela, but recent surveys have failed to record the species on Fernandina. It has been classified as critically endangered by BirdLife International, with an estimated population of 20–40 mature individuals in 2021, located in two large mangroves on Isabela. A study has shown that the two small populations remaining on Isabela Island have begun undergoing speciation and that one or both populations will eventually become extinct due to a lack of interbreeding.
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