The 2002 set issued by Namibia showing its Ephemeral Rivers had 3 stamps which obviously had birds on them, including the $3.50 value with 5 species. Recently, a correspondent in Namibia pointed out that the Elephants stamp in the same set has a bird of prey perched in the tree. The image is very small but an enlargement shows that, of the birds of prey found in Namibia, the two most likely are Black-breasted Snake-Eagle (Circaetus pectoralis) and Martial Eagle (Polemaetus bellicosus).
The artist, Helge Denker, was asked about this bird, and confirmed that it could be either of these two species, and we would just have to wait for it to fly off! He has previously confirmed the identity of the species on the $3.50 stamp, so he is not being unhelpful. Research I have made suggests a Martial Eagle would typically perch at the top of the tree, and my correspondent maintains that the area and habitat suggests that the bird is a Black-breasted Snake-Eagle. I shall include it in my main collection at the end of the month.
The stamp won for Namibia the 8th World Stamp Cup 2003. To celebrate this, the stamp was issued in a MS in 2003.
If anyone would like to comment on this proposal, please email me.