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Landbird Conservation and Control of the Parasitic Fly, Philornis downsi
Charles Darwin Foundation, Galapagos National Park Directorate, SUNY-ESF, Sabine Tebbich (University of Vienna)
Knowledge of Galapagos landbirds, including population size, health, and breeding success, has never been complete. In recent years, populations of several species — including the mangrove finch, vermilion flycatcher, woodpecker finch, and small, medium, and large tree finches — have declined on some islands. Some have gone extinct.
The reasons for these declines are not completely understood, although the biggest threat to landbirds is the invasive fly, Philornis downsi. This parasitic fly feeds on the blood of nestlings, resulting in high levels of fledgling mortality. Other reasons for these population declines may include:
To reverse the decline of small landbirds as quickly as possible, the Galapagos National Park Directorate (GNPD) and the Charles Darwin Foundation (CDF) — with the support of Galapagos Conservancy — are investigating multiple options simultaneously to protect these iconic species. Two international working groups, formed in 2012, developed strategic action plans identifying priority research for the conservation of landbirds and the control of Philornis.
The long-term goals are to:
As of 2018, the landbird group continues to be led by Dr. Birgit Fessl, and the Philornis group is led by Dr. Charlotte Causton, both of the Charles Darwin Foundation. Both working groups meet every two years to reassess the progress of the two action plans, identify additional research topics, and agree on a priority research agenda.
Landbird research includes evaluating the status of Galapagos landbird species, especially on the human-inhabited islands of Santa Cruz, Isabela, San Cristóbal, and Floreana, and developing strategies to detect and respond to species declines in a timely manner. Studies on the ecology of little-known species are also being carried out. The goal is to develop plans for protecting the most threatened landbird species in the Islands.
The mangrove finch (Camarhynchus heliobates) is the bird species most threatened by extinction in the Galapagos Islands. It is classified as Critically Endangered on the International Union for the Conservation of Nature’s (IUCN) Red List of Threatened Species, as fewer than 100 mangrove finches remain. The entire world population lives in two large mangrove forests on the northwestern coast of Isabela Island. As with other landbirds, the primary threat to the mangrove finch is the invasive avian parasite Philornis downsi. In 2014, researchers from the Charles Darwin Foundation (CDF) and the San Diego Zoo Global (SDZG) implemented a captive rearing program for mangrove finches, which will be continued for several years, with the long-term goal of restoring the population.
In 2018, Galapagos Conservancy funded research on the vermilion flycatcher, carried out by Dr. Sabine Tebbich of the University of Vienna, Austria. Recently, two subspecies of the Galapagos vermilion flycatcher were elevated to full species status. Unfortunately, the Least Vermilion Flycatcher, found only on San Cristóbal Island, has not been recorded since 2008, and is believed to be the first modern extinction of a Galapagos bird species. The Little Vermilion Flycatcher, originally found on eight islands, has recently gone extinct on Floreana and is threatened with extinction on Santa Cruz. The populations on uninhabited islands appear to be healthy and have recovered on islands where rats were controlled. Experiments suggest that vermilion flycatchers are better able to withstand parasitism by P. downsi, when food quality is high, and food is abundant.
Dr. Tebbich has focused her research on three populations of vermilion flycatcher (VF):
Philornis downsi is a blood-feeding, parasitic fly that was accidentally introduced to Galapagos (first discovered there in 1997), most likely from mainland Ecuador. It causes high levels of mortality in several species of endemic birds, including the critically endangered medium ground finch and mangrove finch. Mortality is caused by blood loss to nestlings, and the presence of Philornis in a nest often results in 100% mortality of nestlings.
As of 2017, the Philornis working group included 21 institutions from 9 countries. The group is focused on studying the biology of P. downsi and developing methods to control it.
Research projects focus on three areas:
Galapagos Report 2015-16: Biodiversity & Ecosystem Restoration section, see:
Photo credits, from top: Captive-reared mangrove finch hatchling © Juan Carlos Avila/CDF; adult mangrove finch © Francesca Cunninghame/CDF; vermilion flycatcher © Robert Ondrovic; deceased nestling from P. downi © CDF.
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