Since the numbers are based on the mathematical models, they may be somewhat erroneous or imprecise, he added. In order to keep the ground finch out of risk, pest control strategies are needed.
Researchers fear the fly, Philornis downsi, could also lead to the extinction of less common species.
Introducing fly-parasitizing wasps, removing chicks from nests for hand-rearing, and the use of insecticides are some of the approaches suggested by the study.
Newborn medium ground finches are too tiny, at about the size of a peanut M&M, to survive the fly larvae, say researchers. There are an estimated 500,000 individuals throughout the entire island chain.
Speaking to the Daily Telegraph, professor Koop said the flies were first spotted in the islands in 1964 but it wasn't until 1997 that they first showed up in a nest. A 40 percent reduction in infested nests would extend the dire 50-year extinction timeline to more than a century. The possible obstacles are that the wasp has to be host-specific.
A press release from the University of Utah outlining the details of the study can be found here.
To calculate the birds' extinction risk, the researchers used a mathematical model in which they entered five years worth of data. "They were important to Darwin because they helped him develop his theory of evolution by natural selection".
One of the most common species, the mangrove finch, is already facing potential total extinction because it lives in only two populations on a single island.
"They are maggots basically, is what they are", said Prof Dale Clayton from the University of Utah, the senior author on the study.
Larvae of parasitic nest flies that infest Darwin's finches in Ecuador's Galapagos Islands are
It was the beaks of Galapagos finches that helped Darwin to formulate his theory of evolution.
According to researchers, the parasitic fly that appeared on the Galápagos Islands just a few decades ago could wipe out the finch populations.
Those finches that had long beaks ate seeds from within cacti. Alternatively, he also said the birds could evolve a defense mechanism through natural selection that would make the flies, specifically their larvae, less harmful. Around 270,000 of these birds are found on Santa Cruz island.
There are between 14 and 18 species of finch on the Galapagos.
The flies are believed to have arrived in the Galapagos in the 1960s. Those in infested nests usually die within a week of hatching.
The researchers gathered information over five years on fly damage due to finch reproduction. The first pictured that the finch species will have some good years with a lot of food supplies and optimum weather for reproduction. In years were there is either extreme rainfall or dryness, survival rates fall. It lays eggs in the finches' nests. In the worst scenario, the birds would be gone in 50 years. That way, females that mate with infertile males would not produce offspring and the populations would decline. If not for the flies, the end of the finches could be in store due to some other outside factor as human development and environmental degradation have set in motion what is being referred to as the Sixth Extinction.
The simulations then included nine variables. They explained that these flies lay the eggs of their larvae in the nests of the finches.
"That happens in other animals", he said.