Why Fowl Nests Appeal to Flying Bugs and Parasites

Parents visit chicks. Photo credit: Santiago Merino / Madrid National Museum of Natural History

Researchers in Spain are studying how disease vectors such as flying mosquitoes perceive differences in gas concentrations in order to localize their hosts.

Flying insects and parasites are often disease vectors, but a mosquito must find someone before it can bite it. In a study recently published in Frontiers in Ecology and Evolution, researchers examined bird nests to understand how insects and parasites detect gases such as carbon dioxide and methane to locate their hosts.

The researchers focused on bird nesting boxes for blue tits in a deciduous forest in central Spain. They found that the nests contained more biting mosquitoes when the carbon dioxide levels in the nest were higher than in the forest air. “This is important because biting mosquitoes are the main vector of Haemoproteus, the most common blood parasite that infects birds in our study area,” says Dr. Santiago Merino from the National Museum of Natural History in Madrid, one of the researchers on the study.

Begging chicks. Photo credit: Santiago Merino / Madrid National Museum of Natural History

With the threat of climate change looming, the rise in carbon will affect every aspect of our ecosystem – from the largest to the smallest organism. “Predictions predict an increase in diseases in northern latitudes due to climate change,” he says. “But factors like gas concentrations and temperature can also influence the occurrence of diseases.”

Feed the chicks. Photo credit: Santiago Merino / Madrid National Museum of Natural History

The first step in understanding the future is of course to study the present. “We want to know how the relationship between gas concentrations and parasite attraction changes,” says Merino, “in order to adjust our predictions about the spread of diseases.”

Bird breeding caves offered a unique opportunity to study the interaction between gas concentration and parasites, as the enclosed space allows better comparisons. In addition to the positive correlation between carbon dioxide and biting mosquitoes, Merino and colleagues found that there were more mites in the nests when carbon dioxide was higher and more black flies when methane was lower. The methane concentration may be related to bacteria in the nesting materials.

The authors also considered variables such as temperature, brood size and time for their analyzes. If there were no nestlings in the nesting boxes, the carbon dioxide concentration in the nest was not significantly different from the forest air, indicating that the presence of nestlings caused gas fluctuations.

Merino says the relationship between humidity and gas concentration is important and, while explored in this study, it should be further explored. While the study’s focused approach is limited, the authors would like to collaborate with other researchers working in different settings to see if their results differ in other conditions.

Reference: Francisco Castaño-Vázquez, Santiago Merino, Soledad Cuezva and Sergio Sánchez-Moral, August 5, 2020, Frontiers in Ecology and Evolution.
DOI: 10.3389 / fevo.2020.00258