Parasites pose new threat to Darwin`s finches
…accidental introductions of flies…Cambridge, UK, Friday 8th November 2002 -- BirdLife International today warned that Darwin`s finches - made famous by Charles Darwin`s theory of evolution - are facing a new and, for some species, potentially major threat from parasitic fly larvae which feed on nestling birds in the islands of the Galapagos archipelago, Ecuador.At least three species of fly known from South America are thought to have been accidentally introduced in food imports from mainland Ecuador, the first having been identified in 1997. A paper published in the last issue of the ornithological journal, Ibis, reports on nesting success and nestling mortality of 12 native and introduced bird species affected by the flies` parasitic larvae, including seven of the 13 Darwin`s finch species, each of which were found to have the new parasitic fly larvae in their nests.The potential impact of the newly discovered parasites may be major, and further study of the scale of the threat is urgently required, says Birgit Fessl of the Konrad Lorenz Institute, one of the paper`s authors. Most worrying is the presence of these new parasites on Isabella Island, the only place in the world where the Critically Endangered Mangrove Finch Camarhynchus heliobates occurs. This is the most threatened of the Darwin`s finches and numbers 110 individual birds in the wild, says BirdLife International`s Dr Nigel Collar, author of Threatened Birds of the Americas [5,6]. A decline in nestling survival resulting from these new parasitic fly larvae would severely threaten this already critical species with extinction.Although parasites that have evolved a host-parasite relationship often do not seriously harm their host populations, those brought into parasite-free populations often cause severe harm before defence mechanisms evolve. Some have caused avian extinctions. For example, in the Hawaiian Islands, USA, the accidental introduction of the mosquito Culex pipiens fatigans in the 19th Century, a vector for avian malaria, led to the extinction of several endemic bird species, including the Kaua`a `O`o Moho braccatus, `Akialoa Akialoa obscura and Hawai`i Mamo Drepanis pacifica, said Dr Collar. More recently, White-rumped Vulture Gyps bengalensis, Slender-billed Vulture Gyps tenuirostris and Indian Vulture Gyps indicus have declined dramatically in Asia by over 90% since 1994, and are now classified as Critically Endangered by the IUCN Red List of Globally Threatened Species. These declines are strongly believed to be linked to an as yet unidentified disease.On the Galapagos island of Santa Cruz the researchers found that 97% of the endemic finch nests studied were infected by the fly ectoparasite Philornis downsi, with an average of more than 23 parasites per nestling and a relatively high nestling mortality of 27%. Although the researchers say it is difficult to be certain that parasites caused nestling deaths, malnutrition did not appear to be a factor and infestation may have severely weakened nestlings because birds with holes in the back, neck and under the wings were discovered.BirdLife International has today written to the Ecuadorian Environment Minister, Lourdes Luque, alerting the Government in Ecuador to this new threat to Darwin`s finches, and requesting that it prioritise research into the impact of the new parasites and consider improving bio-security measures to help prevent further accidental introductions of exotic parasitic insect species to the Galapagos archipelago.
4th July 2014