Bird lovers who set out seed and water for wild birds in their gardens may be unknowingly helping a dangerous parasite spread between species, according to research published in the journal Molecular Ecology.
Trichomonas gallinae is a single-celled parasite that causes trichomonosis, a disease that can be lethal to a wide range of bird species. It primarily infects the throat and upper digestive tract, forming visible lesions that make eating and drinking increasingly difficult. In severe cases, infected birds can suffocate or starve as the parasite blocks their airways and esophagus.
The study found that shared feeding and watering stations create ideal conditions for the parasite to jump between species. Birds of different types congregate at these points, exchanging saliva and contaminated water, which allows Trichomonas gallinae to move freely among populations that might not otherwise come into contact. Researchers described the parasite as widespread among backyard and wild bird communities where such stations are common.
While the disease has long been associated with pigeons and doves, the new findings suggest it affects far more species than previously thought, including finches, songbirds, and raptors. Outbreaks have been documented in European house sparrows, North American finches, and various passerine species, with mortality rates that can reach very high levels in concentrated groups.
Experts note that the practice of feeding wild birds is enormously popular, particularly in urban and suburban areas, and has grown even more during recent years as more people spend time in their gardens. Ornithologists are now urging caution, recommending that feeding stations be cleaned regularly with disinfectant, water dishes be changed daily, and birds showing signs of illness — such as lethargy, swollen faces, or difficulty swallowing — be reported to local wildlife authorities.
The research highlights a growing tension between conservation enthusiasm and disease ecology. While providing food and water can be a meaningful way to support bird populations, especially in harsh weather, scientists stress that doing so without understanding the disease risks may inadvertently cause more harm than good.
