How are birds impacting local diseases?

Most people think of ticks as a problem lurking in tall grass or in the woods. Something you may not know is that the birds in your own backyard could be quietly transporting disease carrying ticks across towns and states. A new study from Fordham University indicates just how important birds are in shaping the landscape of tick‑borne disease and what that means for public health in the Northeast.

The research examined blacklegged ticks collected from wild birds in 2010 and again in 2019, testing them for three major pathogens: Lyme disease, anaplasmosis, and babesiosis. These diseases are already prevalent in the Northeast, and cases have risen steadily over the past twenty years. As the authors note, “cases of tick‑borne disease… have grown and record numbers have been reported in the United States in recent years.” Birds, with their ability to fly long distances, have been found to carry ticks very fast and to new areas as well.

One of the study’s most significant findings is that the number of ticks on birds that carry Lyme disease has almost doubled over the past decade, rising from 17.2% in 2010 to 33.8% in 2019. While this isn’t the main focus of the paper, it’s a notable change that indicates more general ecological changes, such as changes in bird migration or population. On the other hand, anaplasmosis showed the opposite trend, dropping from 9.7% to 2.9%, while babesiosis began appearing in 5.1% of ticks in 2019. Even though these numbers are smaller, they are still meaningful as they demonstrate that not all tick-borne pathogens are affected in the same way.

Not all birds contribute equally. Some species appear to be especially important in sustaining and spreading pathogens. The study found that American robins and Carolina wrens carried ticks with higher rates of infection in 2010, while Carolina wrens, northern house wrens, and veeries stood out in 2019. These birds are commonly found in neighborhood yards and parks. Their habits bring them into contact with ticks during peak larval season, and their mobility allows them to disperse ticks far beyond where they picked them up.

Climate change makes this situation even more complex. Warmer temperatures can extend tick activity seasons, shift bird migration timing, and alter habitat use, all of which influence where ticks and pathogens end up. The study doesn’t model climate directly, but its decade long data also reflects a period of rapid environmental change. Migratory birds, in particular, can carry ticks across geographic barriers. As the authors note, birds “provide a unique opportunity for substantial tick and pathogen dispersal.” This includes areas that have not been established yet.

This research highlights how complex and interconnected tick‑borne disease ecology truly is. Understanding the role of birds helps scientists better predict where risks may rise next and how pathogens move through the environment. The message for individuals is that tick exposure isn’t limited to hiking trails, so it is important to be aware of ticks, even in suburban or backyard environments.

About the research:

Pandey, M., Clark, J. A, Piedmonte, N. P., Zolnik, C. P., Pool, J. R., Daniels, T. J., & Hekkala, E. (2025). Temporal changes in the prevalence of three disease-causing pathogens in bird-borne blacklegged ticks: Borrelia burgdorferi sensu stricto, Anaplasma phagocytophilum, and Babesia microti. Ticks and Tick-Borne Diseases, 16(5), 102537.