In the past few years, the Galapagos birds that helped inspire Darwin's theory of evolution by natural selection have hit hard times. A parasitic fly has brought their population numbers to dangerous new lows. This threat could wipe out Darwin's finches within 50 years. However, a new study suggests that certain preventative measures could help these rare birds gain back some ground in the islands.
Published today in the Journal of Applied Ecology, the collaborative study examined three viability models based on five years' worth of data on Geospiza fortis, or the medium ground finch, one of the islands' more common species. The goal was to determine the birds' longterm outlook for survival while plagued with parasitic Philornis downsi flies. Introduced to the islands by human visitors, the flies begin life as larvae hatched from eggs laid in the nests of Galapagos finches, and spend their first days eating away at the inside of baby finches' nasal cavities before migrating to the bottom of nests and emerging at night to feed on chicks' blood, Yale Environment 360 explains—a process that kills young finches or leaves them with deformed beaks, making it difficult for them to feed themselves.
University of Utah biology professor Dale Clayton, the study's senior author, noted in a press release that two of three viability models tested showed that the fly could potentially drive this and other finch species into extinction within the next several decades, but that the team's results were not "all doom and gloom." He explained, "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."
Voyage of the Beagle, 1845. Image credit: Wikimedia Commons // Public Domain
Methods of human intervention that could help save the approximately 14 to 18 species of Darwin's finch include removing chicks from nests for safer hand-rearing; releasing sterile male flies and fly-parasitizing wasps into the islands' ecosystems; and even getting finches to pitch in by self-fumigating their own nests. The latter idea comes from a 2014 study Clayton did in which researchers set out cotton balls treated with the mild insecticide Permethrin, hoping the finches would use the cotton in nest-building. They did. In the nests with Permethrin-treated cotton balls, half of the fly larvae died, Phys.org reported. "We are trying to help birds help themselves," Clayton told the site.
Jennifer Koop, an assistant professor of biology at the University of Massachusetts Dartmouth and the study's first author, noted that a 40 percent reduction of flies in finch nests could extend the birds' predicted extinction date from being several decades away to perhaps a full century, during which time finch populations would have more time to adapt and recover. If that goal could be met, she said, researchers "predict they will no longer go extinct."
Koop also stressed the importance of keeping these rare and uniquely illustrative birds around. "Darwin's finches are one of the best examples we have of speciation," she said in a release. "They were important to Darwin because they helped him develop his theory of evolution by natural selection."