On 9 May 2000 Luxembourg issued four new stamp series. The topics are ducks, Europe, Robert Schuman and natural gas. The male is easily recognisable with its yellow bill, green head and blue speculum on its wings.
Mallards breed almost on every pond and river throughout Luxembourg.
The mallard is a dabbling duck, that means that it never completely dives under water when feeding. Pochards are diving ducks that spend much time diving for food. The female has a uniform grey-brown plumage and is not so distinctive. In good light, the dark feathering shows sheen and the yellow eye and the small crest features may be seen. The theme of the stamps, designed by the French artist Jean-Paul Cousin, was selected from proposals submitted by the organisation's members, and accepted at the PostEurop plenary meeting held in 1998 in Monaco.