A project to study the impact of pollution on the acoustic quality of birds is being undertaken at the National Zoological Park.

The project is being undertaken by the students of Delhi University at the zoo that houses around 642 birds of 51 different species (as per 2015 inventory report).

"Delhi zoo with its rich diversity of birds and animals has always been a destination for various environmental projects. The avian project will record the sounds of birds here in order to gauge the impact of pollution on their acoustic quality," a zoo official said.

Ankita Das, final year Environmental Science student of the DU who is part of the project, says, "Birds generally produce low frequency sounds so that these signals travel long distances and reach their mates or other birds. But due to the rising pollution level, there has been a sharp increase in their frequency levels."

"Delhi is only second to Kenya with a rich diversity of birds despite having high levels of noise pollution. The project tries to decipher the connection between pollution and acoustic quality of birds further," she said.

Das explains how human settlement and environment quality of an area affect the acoustic level of birds.

"There are many interesting facts about birds. For instance, the indigenous birds rarely perch on exotic trees. Their sound levels can vary from place to place depending on the plantation and human settlement," she says.

The DU student, an avid bird watcher since childhood, says 6 am to 8 am and 5:30 pm to 6:30 pm is the best time for observing the sound of birds.

"Though birds are active throughout the day, early morning and evening time is apt to record the avian sounds. In other words, as the day passes and the sun grows stronger, the ground heats up and the sounds get refracted or dispersed," she says.

The project is also being undertaken at other places in the city, including DU campus, Sanjay Jheel, Lodhi Garden, district parks etc.