City noise affects health and birdsong

Urban traffic noise causes learning deficits and delays in young birds. These birds also have weakened immune systems, a sign of chronic stress.   Traffic noise is ubiquitous in our cities. While it is an integral part of the urban landscape, it is not without consequences for the body. This noise pollution harms the health and well-being of millions of people and animals living in cities. Constant noise can indeed cause serious illnesses in adults, and even learning disabilities and language deficits in children. To analyze in greater depth the mechanisms linking chronic noise exposure to cognitive impairments, researchers at the Max Planck Institute for Ornithology, in collaboration with the Universities of Paris-Nanterre and Manchester, studied song learning and immune functions in young zebra finches exposed to urban traffic noise. Like children, songbirds must learn to vocalize from adults, but this is only possible during a short period early in their lives. Under normal conditions, the song of young zebra finches develops and stabilizes around 90 days of age, then remains the same for the rest of their lives. This process is called “crystallization.” However, when juveniles are exposed, during this critical period of their development, to traffic noise recorded near heavily trafficked roads in Munich, deficits in their song learning emerge. Their adult song—known as “crystallized”—is acquired more than 30% later than in birds raised in a quiet environment, and with much less characteristic vocal precision. But that’s not all. Researchers have discovered that urban noise also weakens the immune response of young birds, suggesting that it is a source of chronic stress in developing juveniles. Just like children, young songbirds are therefore particularly vulnerable to the effects of ambient noise, which can impair their learning abilities during successive acquisition phases. The consequences are significant, as the development of the birds’ vocal repertoire is disrupted. Errors in learning and memorizing songs caused by urban noise accumulate with each new generation. These findings mark a new milestone in the study of the effects of anthropogenic noise on human health and well-being. In particular, they establish that bird song can be used as an experimental paradigm for future studies on noise-related cognitive and developmental disorders, particularly with regard to impairments in vocal learning and speech development.