A pair of researchers has found that noise pollution prevents songbirds from hearing and responding to alarm calls. Anthropogenic noise makes it difficult for them to hear alarms, leaving the birds vulnerable to predation. The details are in a paper that was just published in The Condor: Ornithological Applications.
Anthropogenic noise is a form of noise pollution caused by human activities. This type of pollution can disrupt communication between animals; previous research has already demonstrated this effect with whales and other marine mammals. There has been very little research on how noise pollution affects terrestrial animals and birds.
Two researchers from Vassar College in New York designed an experiment to observe how birds would respond to alarm calls by the tufted titmouse (Baeolophus bicolor) in situations with added traffic noise. The tufted titmouse is a small songbird in the chickadee family. They have a well-known “chick-a-dee” alarm call that informs other birds of incoming danger. The researchers recorded these calls and set up speakers near bird feeders. Once the bird feeders were baited, they played back the calls—either with or without anthropogenic noise that was recorded locally.
The researchers found that very few birds approached the speakers when the alarm calls were mixed with anthropogenic noise. The addition of noise pollution to “chick-a-dee” alarm call recordings caused an 80% decrease in the number of birds who approached the speakers. The added noise didn’t deter birds from feeding but caused them to ignore alarm calls. This is a problem because songbirds might continue to forage in noisy areas, failing to recognize alarm calls that would warn them of danger. This might make songbirds more vulnerable to predation, especially when the birds are in high traffic areas with a lot of human activity.
The findings suggest that anthropogenic noise can mask alarm calls, causing songbirds to continue feeding in dangerous situations. When the researchers played alarm calls with added noise, most birds ignored the warnings and kept foraging. More research is needed to fully understand the ecological impacts of anthropogenic noise.
Gall, Megan and Jacob Damsky. Anthropogenic noise reduces approach of Black-capped Chickadee (Poecile atricapillus) and Tufted Titmouse (Baeolophus bicolor) to Tufted Titmouse mobbing calls. The Condor: Ornithological Applications (2016).