Menu

Invasive Parasitic Fly Threatens Future of Unique Galapagos Land Birds

The Galapagos Islands are famous for their spectacular species of birds. They first came to the attention of the world after Charles Darwin first collected specimens on the archipelago in 1835, helping him later by providing clues to develop the theory of evolution. The islands’ birds have captivated the imaginations and inspiration of explorers, sailors, scientists, and tourists ever since. These iconic animals are one of the main reasons many thousands of visitors come to these islands each year. But having evolved into their Galapagos niches over countless generations, the birds of Galapagos are facing a deadly enemy, an invasive insect that preys on chicks in their nests.

Figure 1 - Male Vermilion flycatcher inside the crater of Alcedo volcano on Isabela Island, eating a worm close to an active fumarole.
Figure 1 – Male Vermilion flycatcher inside the crater of Alcedo volcano on Isabela Island, eating a worm close to an active fumarole.

In the mid-1990s, scientist Birgit Fessl discovered an invasive parasitic fly (Philornis downsi) in a Darwin finch nest. Since that discovery, many researchers around the world have investigated the fly’s impact on the birds in Galapagos. Initially, the fly visits and lays eggs in birds’ nests. After 1-4 days, the larvae emerge and attack soft tissue of chicks in the nest, causing destructive health problems for the baby birds. Many chicks cannot withstand the onslaught of the larvae and die before ever leaving the nest. This fly has been found in almost all small land birds in the Galapagos, causing reductions in breeding success, producing deformation of nasal cavities and tissue damage. At the current rate of parasitism, Philornis is a highly dangerous threat for small birds in Galapagos.

Searching for a Solution

To combat this threat, the Charles Darwin Foundation is leading a multi-institutional project to find a way to control the fly and protect the birds. Through collaborations with the Galapagos National Park, the Landbird Conservation Project monitors populations of various land bird species across the different islands. The project conducts censuses to determine numbers of individuals in specific areas and utilizes this information to track population changes. The critically endangered mangrove finch is heavily affected by this fly; only around 80 individuals remain. The Vermilion flycatcher populations in Galapagos are also decreasing drastically on different islands, with one of the main threats being the fly.

Small-scale techniques to control the infestation of the Philornis fly in a small number of nests are currently being tested to help the Galapagos birds survive until a definite way to control the fly is discovered. One of the most promising solutions is biological control, where parasitoids of the fly could be introduced to the islands. We are currently working to develop other methods as well, including development of odor traps to capture flies and decrease their populations. A highly dedicated group of scientists from the Landbird and Philornis research departments are fighting hard to protect and save the unique birds of Galapagos.

Many large Philornis larvae, which are collected in nests of Galapagos birds, decrease the chance for the baby birds to survive. The larvae are raised to adult flies to conduct odor experiments in the Charles Darwin Foundation Lab.
Many large Philornis larvae, which are collected in nests of Galapagos birds, decrease the chance for the baby birds to survive. The larvae are raised to adult flies to conduct odor experiments in the Charles Darwin Foundation Lab.

image001David Anchundia is an ornithologist for the Galapagos Landbird Conservation Program at the Charles Darwin Foundation. Initially, he worked in the Galapagos supporting research on sea lions and fur seals. David received his Master of Science working with the blue-footed booby, incorporating GPS tagging, bird counts on coastlines, and feeding ecology. Currently his research focuses on the iconic Darwin’s finches and flycatchers in Galapagos. The Landbird Conservation Program aims to provide basic information about population sizes of birds across Galapagos and to gain scientific information on poorly documented species like the Vermilion flycatcher. David’s research aids in efforts to save Galapagos birds from an invasive parasitic fly.

The birds of Galapagos tweet… why don’t you? Re-tweet my post to help save the birds!

References

Fessl, B., & Tebbich, S. (2002). Philornis downsi–a recently discovered parasite on the Galápagos archipelago–a threat for Darwin’s finches?. Ibis,144(3), 445-451.

Dudaniec, R. Y., & Kleindorfer, S. (2006). Effects of the parasitic flies of the genus Philornis (Diptera: Muscidae) on birds. Emu106(1), 13-20.

Cunninghame F. (2012) Landbird Conservation Plan: Strategies for reversing the decline of passerine birds on the Galapagos Islands. CDF reports