A recent study conducted by researchers at the University of California, Berkeley, has revealed that birds are significant hosts of the bacterium Borrelia burdorferi, which is responsible for Lyme disease. The disease is most often associated with being spread to humans from bites by infected ticks.

The spreading of Lyme disease has been previously linked to small mammals such as wood rats and squirrels, but the new study, published in the journal PLOS ONE, is one of the first – and certainly the most comprehensive – to look at the role of birds as hosts for the bacteria.

The study’s lead author Erica Newman said that the link between birds and the endurance of Lyme disease bacteria is “poorly understood.” Newman, a UC Berkeley PhD student in the Department of Environmental Science, Policy, and Management, added, “This is the most extensive study of the role of birds in Lyme disease ecology in the western United States, and the first to consider the diversity of bird species, their behaviors and their habitats in identifying which birds are truly the most important as carriers.”

Some species of the Lyme-carrying birds identified included American robins, golden-crowned sparrows, and dark-eyed juncos, which are often found in large numbers in suburban areas. To produce their findings, researchers analyzed bird and tick samples gathered from four different sites within the UC Hopland Research and Extension Center in northwest California. It was found that 57 of the 100 birds that carried ticks also carried the Lyme disease bacteria.

Morgan Tingley, an ornithologist unconnected to the UC Berkeley-led study, said, “Birds are much more capable of carrying diseases long distances than the small-mammal hosts typical of Lyme disease, and so may constitute an underappreciated component of Lyme disease ecology.”

Tingley added a caution for future researchers: “Particularly as we look to the future, birds may end up playing a larger role in disease ecology than other animals because of their ability to quickly and easily move long distances and to new habitats. In the same way that airplanes can help spread disease across nations, birds do the same thing for our ecosystems.”