The RSBP has launched a direct-mail pack as the second step in a continuing campaign to try to halt Government proposals for a new airport twice the size of Heathrow at Cliffe in the North Kent Marshes.
The marshes, which are beside the Thames Estuary, provide a habitat to 200,000 wading birds, ducks and geese, and the area is protected under national and international law because of its importance for wildlife.
"We are urging people to support our campaign against this proposal, which would be a disaster for people and wildlife," said the RSPB's PR manager Liz Rose.
The campaign began six weeks ago with a mailing sent to the RSPB's one million-plus membership. This latest stage targets non-members in areas affected by the proposed development with a direct-mail pack and will be followed by a series of initiatives in the coming months.
The mail pack has been sent to 35,000 people in north Kent and is designed to promote local action. It contains a protest postcard to be sent to the Department for Transport, a campaign newsletter and a window poster and stickers.
The protest postcards come in two sections to help the charity monitor the success of the cards. One part is marked for the Government and the other will go to the RSPB.
"It will be difficult to gauge the response as we don't expect everyone to send the accompanying card back to us," said the RSPB's head of PR, Paul Lewis. "The most important thing is that they send it to the Department for Transport."
The newsletter also promotes a range of 'No airport at Cliffe' merchandise, including T-shirts, caps, mugs, badges and soft toy avocets (one of the birds that would be affected by the airport). A billboard campaign is expected to start in June.