When Peru issued a set of four stamps celebrating the wildlife of the Paracas National Reserve and used photographs, it was not
too surprising that a bird other than the target species would be found. On the stamp showing a colony of Peruvian Boobies
(Sula variegata), I noticed a dark bird, out of focus, flying away from the camera. Its dark wings have white trailing
edges on the inner half, and the black tail is forked. Checking species likely to be found in such a colony, I soon found
that Inca Tern (Larosterna inca) had these features.
Inca Terns are endemic to the Humboldt Current off the west coast of South America, along with several other species found only in this restricted habitat. See The Peruvian Seabirds Home Page.
An inferior image of the species appeared on a stamp from Antigua & Barbuda issued in 1998 - Seabirds of the World, and a better image more recently on one from Mozambique. So this is the first to appear on a stamp issued by a country where the species is native.
Although the set of stamps bears "2001", according to StampCafe.com, it was issued 21 May, 2002.
If anyone would like to comment on this proposal, please email me.