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Nestling Birds

Researchers from a Canadian university have found that noise from human activities can drown out the vital communication link needed between nestlings and parent birds meaning they are unable to differentiate between feeding calls and alarm calls.

Baby birds are totally dependent on their parents for both food and protection and vocal communication helps nestlings determine when they should beg for food and when they should crouch in the nest and keep quiet to avoid predators.

However, a group of researchers from Dalhousie University in Halifax, Nova Scotia has found that ambient noise from traffic, building construction, industry and other man-made activities disrupts this communication which can leave nestlings hungry and vulnerable. They have suggested that spreading urbanization is having a negative impact on birds’ well-being, not just from destruction of their habitat but from their proximity to built up areas.

Nestling birds face tough competition from hungry siblings and will instinctively react to any sign that a parent might have food, vigorously begging to attract attention. Although this rapid response increases the chicks’ chances of getting fed, in their haste they may incorrectly identify a predator instead of a parent. Conversely if cautious nestlings fail to hear their parents approaching the nest they miss out on a vital meal.

The team from Dalhousie University suspected that nestling birds’ exaggerated begging calls might not just be an overly dramatic plea for attention but an attempt to convey an important message over background noise.

They tested their hypothesis by playing audio recordings of a parent bird warning of a predator or announcing a delivery of food to baby tree sparrows and compared the young birds’ responses to the sounds when coupled with recorded background noise or in a quiet environment.

The researchers found that background noise reduced the responsiveness of nestlings to both feeding calls and alarm calls. They often failed to beg in response to the feeding calls and continued begging instead of falling silent in response to the alarm calls. The team also found that parents did not appear to change their calls in noisier situations.

Although not all ambient noise comes from human activity, a large housing development or busy motorway generates a more persistent noise than natural phenomena such as wind and rain.

The study backs up previous research carried out by a team from the University of Sheffield which showed that noise in urban areas could be increasing the mortality rate of young house sparrows by interrupt the communication between young birds and their parents.

Professor Andrew Horn who led the study said. "We usually associate declines in animal populations with our physical destruction of habitat, but the noise we make is another threat that we can't ignore.”The team will continue their studies hoping to determine which sounds are particularly detrimental to communication between parents and nestlings.

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