Kites flying activity in the run up to Vishwakarma Puja has taken a heavy toll on birds across the city.

More than 30 birds with kite string injuries have been rescued since Wednesday by the forest department’s wildlife rescue teams as well as individuals across the city, an official at the Wildlife Rescue Centre in Salt Lake said on Thursday.

Birds struggle to free themselves after they get caught in the strings and in the process injure their wings, legs or talons. Some even die.

According to the forester, the centre had been receiving calls from across the city and even from the outskrits to resuce injured birds.

Manja (a mixture of glass and glue) helps kites soar but also adds to the string’s sharpness. Such strings do not snap and leave birds, entangled in them, severely injured.

The nylon ones are known as Chinese manja — they are almost unbreakable and extremely sharp.

Calcutta High Court had in July directed cops to strictly enforce the ban on Chinese manja. However, they are easily available in the markets.

Suprakash Mukherjee, a resident of Manicktala who has been flying kites with his son, said the Chinese manja was quite popular as during kite fights. “If you are using Chinese manja then your kite becomes near invincible....although it is extremely hazardous for two-wheeler riders as well as birds,” said Mukherjee.

The Telegraph had earlier reported how kite sting injuries were getting increasingly common as birds would fly into dangling strings.

Soumyodip Mukherjee, an IT architect, rescued a dove that was dangling from a piece of kite string in Phoolbagan.

“It was a piece of nylon string. We had to cut through with a knife to get the bird down,” said Mukherjee.

Kalyani resident and bird lover Diptimoy Pal, drove down to Dankuni, a distance of around 45km, to help residents there bring down a black crowned night heron that was entangled in a kite string.

Pal will handover the bird to the forest departmnet on Friday morning.

Subhankar Patra, a veteran birdwatcher said that they would often come across these injuries when the season of flying kites starts.

“Birds cannot see the string while flying and they get entangled in them,” said Patra.

Several NGOs that work towards animal welfare have started campaigns on social media asking people not to use nylon strings or glass laced ones while flying kites.

Shamik Dutta, a member of Bonyo, an animal welfare organisation, said they had started a social media campaign as well as helpline number where people can call if they spot injured birds.

A similar campaign has also been started by Society for Heritage & Ecological Research (SHER), an NGO that works to reduce human-wildlife conflict.

“Awareness is the key here,” said Joydip Kundu the founder member of SHER.