I first saw this interesting sheet on Tony Bray's web site, and decided to send for it as soon as possible, to check on the species shown.

I soon realised that many of the paintings are based upon illustrations in Robson's Field Guide to the Birds of South-East Asia. This helped to identify some of the smaller images. The most surprising is the bird in flight at the top of the Pelican stamp, which appears to be Giant Ibis (Pseudibis gigantea) similar to the illustration in the Field Guide. In 1991, a significant number of this species was found in Cambodia.

Update - I overlooked a pair of birds at the top of the heron stamp. I have now added this to the series of small images. Unfortunately, the perforation holes have obliterated part of the heads of both birds, and distorted what is left.

The Ibis and Great-billed Heron are new species for my collection.