Chennai, June 5 -- The Tamil Nadu Postal Department released Special Covers on e-bicycle ride and the invasive Free Vaduvur Bird Sanctuary to mark the World Environment Day (WED) on Thursday.

In India Post, a Special Cover is a philatelic item that is issued to commemorate a special event, person, place, institution or significant occasion.

The purpose of the Special Cover is to document and celebrate important milestones, cultural, historical, scientific, and social events, to promote awareness of a particular cause, personality, heritage site, initiative and to encourage philately among the public, a PIB release said.

This WED, Central Region, Tamilnadu Circle created awareness about clean energy among members of the public by or...