By Will Dunham
WASHINGTON (Reuters) – Which nest is best to eliminate a blood-sucking pest? Scientists seeking to help endangered Galapagos Islands birds survive a deadly parasitic threat put that question to the test.
Researchers on Monday described a new method to assist Darwin’s finches in combating the larvae of parasitic flies responsible for killing numerous nestlings of the famous birds that helped inspire Charles Darwin’s theory of evolution by natural selection.
They placed cotton balls treated with a mild pesticide near where the birds were building their nests. The birds picked up bits of the cotton with their beaks and incorporated it into their nests, killing the fly maggots while causing no harm to the birds or their offspring, the researchers said.
The pesticide was permethrin, used to treat head lice in people. It also kills flies of the species Philornis downsi that was apparently unwittingly introduced by people to the Galapagos Islands and has been blamed for population declines among Darwin’s finches, including two endangered species.
“This parasite is not historically found in the Galapagos Islands and, therefore, Darwin’s finches have not had enough time to evolve defenses against the parasites, ” said University of Utah biology professor Dale Clayton, one of the researchers.
“In some years, 100 percent of nestlings die as a direct result of the parasites. It is critical to find a way to control the parasites in order to help the birds, ” Clayton said.
The flies probably came aboard ships or planes arriving at the Galapagos and were first noticed as a problem in 1997. The flies lay eggs in bird’s nests. When they hatch, the parasitic larvae feed on the blood of nestlings and their mothers.
Finding a method to control the flies has become a top priority for scientists studying the Galapagos birds.
“There are currently no methods to effectively combat the parasite, ” said University of Utah biology doctoral student Sarah Knutie, another of the researchers.
‘SITTING ON MY PORCH’
A casual observation at a research facility in the Galapagos led to the idea of helping the birds help themselves.
Natural selection is the gradual, non-random, process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers. It is a key mechanism of evolution.
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