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ESF Scientists Battle Fly That Threatens Darwin’s Finches

Blood-sucking maggots pose danger to birds in Galapagos

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Researchers from the SUNY College of Environmental Science and Forestry (ESF) are traveling to the Galapagos Islands this month to search for ways to combat a non-native, invasive fly that is threatening native birds, including mangrove finches, one of the species studied by Charles Darwin.

The pest has contributed to reducing the population of mangrove finches to fewer than 100 nesting pairs, said Dr. Stephen Teale of ESF's Department of Environmental and Forest Biology.

"They are on the verge of extinction," Teale said.

He described the fly larvae as blood-sucking maggots.

The flies, in the same family as the common housefly, invade the nests of mangrove finches and Floreana mockingbirds, among others. Females lay their eggs in the nests. First, the larvae crawl into the nasal cavities of young birds to feed, causing beak deformities that can be disabling to the birds that survive. At a later stage in their life cycle, the developing larval flies spend their days in the nest and emerge at night to pierce the birds' skin with paired, hook-like mouthparts and drink the birds' blood. Many of the young birds die from anemia.

The flies, native to the South American mainland, were first found in the Galapagos in the 1960s. They were a problem by the 1990s and within the last decade, Teale said, they have developed into a major threat to the bird populations.

Teale, who has been researching the flies in his laboratory, is traveling to the Galapagos with ESF senior Kristin Doherty. They will attend workshops to do presentations on the research that has been done so far and then begin fieldwork, which will include researching the flies' mating habits, their ability to find the birds' nests and their reaction to food odors.

Teale's work focuses on the chemical pheromones that insects use to communicate. His goal is to identify the chemical structure of the pheromones the flies use as sex attractants. If the chemical compounds can be synthesized in the laboratory, they can be used to trap the flies, which can lead to information about the flies' abundance, location and behavior. The pheromones can also be used to disrupt the flies' mating behavior.

Teale and Doherty will work out of the Charles Darwin Foundation facilities on Santa Cruz Island. The work is funded by the Galapagos Conservancy. An Ecuadorean graduate student will also be part of the research team.