A bird survey is being conducted at the Pench Tiger Reserve (PTR) in Maharashtra as part of the "citizen science" model with an aim to create a baseline data of bird diversity and density, an official said. More than 125 volunteers, in the age group of 18 to 74 years, from 11 states were participating in the three-day bird survey which began on Friday, PTR's deputy director Dr Prabhunath Shukla said in a release on Saturday.