Six species of birds have been introduced to Galapagos, including chickens Gallus gallus), turkeys (Meleagris gallopavo) and Muscovy ducks (Cairina moschata), as well as semi-domestic Rock Pigeons (Columba livia), and wild species such as Smooth-billed Ani (Crotophaga ani) and Cattle Egrets (Bubulcus ibis).
Although not all of these species pose the same level of risk to the native flora and fauna, many of these species can serve as hosts and carriers for introduced diseases and parasites, which may have devastating effects on native and endemic species of animals. Diseases that have caused the extinction of birds in other archipelagos, could be responsible for at least some of the extinctions or decreases in native or endemic birds in Galapagos. Certain diseases could have arrived with domestic birds. In the last two decades, Newcastle disease, Marek’s disease, salmonellosis, coccidiosis, and other diseases have been diagnosed in domestic fowl. During recent years, visiting scientists have confirmed that the tumors present on finches are caused by avian pox, which also affects endemic mockingbirds.
Rock pigeons were introduced to the Galapagos archipelago in 1972-1973 and became well-established on three islands, Santa Cruz, San Cristobal and Isabela. Rock pigeons are carriers of many diseases which affect humans, wild life and poultry. In Galapagos, the rock pigeon is the carrier of Tricomonas gallinae, a fatal disease for poultry and endemic doves.
As populations increased, so did the risk of disease transmission to humans and populations of native birds. It was therefore decided to eliminate the species. The eradication program led by the Galapagos National Park Service (GNPS), with technical support from the CDF, was carried out on all three islands. The abundance and distribution of pigeons was first ascertained using surveys on foot or from a vehicle and locations of birds were recorded by the GNPS. Birds were largely removed and at present, the islands are being continuously monitored in order to confirm control methods have worked, and ensure that any re-introductions from other islands are detected and removed immediately.