What is the state of health of songbirds on the Galápagos Islands?

The land birds of the Galápagos Islands are particularly close to our hearts, as the latest counts by Birgit Fessl and her team have unfortunately confirmed the assessment of the International Union for Conservation of Nature (IUCN) that half of all land bird species in the archipelago are currently endangered. After Floreana Island, Santa Cruz Island has seen the sharpest decline in population. 

As is so often the case, humans are the cause of these problems. Introduced plants and agricultural use are changing the birds' habitat, and invasive species such as the vampire bird fly (Philornis downsi) threaten the survival of bird chicks. In addition, bird pathogens are also introduced to the archipelago by imported poultry or migratory birds. These pathogens are transmitted to native birds, many of which are found only on the Galápagos Islands, posing a further threat to the already declining songbird populations. 

According to the latest findings, emerging infectious diseases pose a major risk to small animal populations living on remote islands such as the Galápagos, as they have not been able to develop defense mechanisms against the pathogens, which can then lead to a drastic reduction in animal populations. 

Back in 2008, both domestic and wild birds on the inhabited islands of Floreana, San Cristóbal, and Santa Cruz underwent health checks. Antibodies to various parasites and pathogens were found in some of the birds, suggesting that these animals had been infected. Unfortunately, no long-term health monitoring of the birds was established at the time, nor were any further studies undertaken.

This would have been important, however, as some of the pathogens detected at the time can have a detrimental effect on the survival of the endemic birds of the Galápagos Islands. They also pose a risk to public health, as some of them cause zoonoses, meaning that the bird disease can also be transmitted to humans. It is therefore important to determine which pathogens are already present on the Galápagos Islands and how widespread they are. The findings can then help to develop effective protective measures to combat existing diseases and reduce the risk of new pathogens being introduced by humans. 

In 2019, sampling of various species of Darwin's finches, mockingbirds, and other songbirds began on the islands of Santa Cruz and Floreana to test for possible pathogens.

Biologist Birgit Fessl and her team were able to test over 400 wild birds and chickens for bird diseases and carry out health checks, taking swabs from the throat, beak, and cloaca of each bird. These samples are now being examined using molecular biology techniques in the laboratory of the Charles Darwin Station (CDF) under the direction of veterinarian Dr. Ainoa Nieto-Claudin, who also led the health analysis project for giant tortoises. Positive samples are sorted out and subjected to further genetic analysis. The tests focus on the following six infectious diseases that could pose a threat to land birds:

The avian adenovirus and Newcastle disease have both already been detected in poultry and land birds. The Newcastle virus is also known to infect humans. In addition, there is mycoplasmosis and Marek's disease, a herpes virus that primarily affects chickens and therefore also poses a risk of transmission to humans. Avian influenza has not yet been detected on the Galápagos Islands, but as it is widespread in Ecuador, the risk of transmission by migratory birds is considered to be very high. In addition, salmonella infection has been detected on poultry farms on Santa Cruz Island in connection with antibiotic resistance, which may pose a threat to public health. 

Comparing the information obtained in this way with data from 2008 will then form the basis for the development of urgently needed basic protective measures for the birds. In the last issue of Galápagos-Intern, we reported that large parts of the land bird population on Floreana Island are currently living in quarantine enclosures because bait is being laid out across the island to eradicate invasive house rats (Rattus rattus).

The tests carried out by Birgit and Ainona's teams are very important for this project, as they will help ensure that the birds are in the best possible health when they are released from quarantine, which is planned for the end of 2023/early 2024, and can be reintroduced to the island.

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