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Darwin's Finches May Face Extinction From Parasitic Flies, But Humans Can Help

Dec 18, 2015 01:20 PM EST
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A species of parasitic flies could wipe out Darwin's finches on the Galapagos Islands in as little as 50 years, according to researchers from the University of Utah. But there is a silver lining: Human intervention and pest control could save these iconic birds that once inspired Charles Darwin's theory of evolution.

"Our mathematical model also shows that a modest reduction in the prevalence of the fly, through human intervention and management, would alleviate the extinction risk," Dale Clayton, biology professor and senior author of the study, explained in a news release.

Finches played a large role in Darwin developing his theory of evolution. During his time on the islands, which are located off the coast of Ecuador in the Pacific Ocean, he noticed that finches exhibited different adaptations to suit the environment they lived in.

For example, Darwin noted several birds living on different islands had different beaks, so he hypothesized some birds had longer beaks to pick seeds out of cactus, while others had smaller beaks to pluck seeds from the ground. His discription of Finch evolutionary adaptations (which continues to be rexamined and debated) lead the famed naturalist to coin the term "natural selection."  

There are between 14 and 18 different species of finches living in the Galapagos, but for the purpose of their study, researchers chose to examine one of the most common: the medium ground finch (Geospiza fortis) -- 270,000 of which can be found on Santa Cruz Island.

The birds' arch nemesis, the parasitic nest fly (Philornis downsi), is not native to the Galapagos, but was introduced to the islands in the 1960s. These invasive flies lay parasitic larvae in finch nests where they attack young birds at night. The flys even lay some larvae directly inside the nostrils of nestlings so when the eggs hatch larvae can immediately begin feeding in the nostrils, which is evident in perforations through the bill and in abdomen lesions, Clayton told BBC. (Scroll to read more...)

(Photo : Jennifer Koop, University of Utah)
A medium ground finch nestling with nostril and abdomen lesions caused by parasitic fly larvae.

But there is hope. In their study, researchers explain several steps that can be taken to save Darwin's finches from extinction. This includes introducing fly-parasitizing wasps, removing chicks from nests for hand-rearing, raising sterile male flies to mate with females so they can't lay eggs in finch nests, and using insecticides, such as pesticide-treated cotton balls that would be placed near the birds so that they can collect them during nest-building and inadvertently self-fumigate their homes.

In addition to human intervention, Clayton added it is possible "there will be a rapid evolutionary response by the birds, and their immune systems would rapidly develop the ability to combat the fly. That happens in other animals," he explained in the university's release. "The question is, will these finches have enough time to develop effective defenses before they are driven to extinction by the fly? It's an arms race."

Their study was recently published in the Journal of Applied Ecology.  

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