Postage stamps are a form of miniature art. It must be difficult to get the many details necesssary onto such tiny pieces of paper ("no bigger than a postage stamp...) so animals on stamps have to be carefully drawn to allow for their proper identification.
There are many themes to follow for avid stamp collectors. Collecting stamps of birds comes under "biophilately" and seems to be pretty popular. One person I've Googled is attempting to collect stamps (from anywhere in the World) that depict a species of bird on the South African national list. He's well over half way to his goal.
ACAP-listed albatrosses and petrels get depicted on postage stamps quite regularly but I have not yet heard of anyone trying to emulate the South African bird stamp collector and collect a stamp for each of the currently 29 listed species. So I have tried to do so myself, although I've restricted my actual collecting to searching on-line for electronic images, mainly at Kjell Scharning's "Theme Birds on Stamps" site at http://www.birdtheme.org/.
Here's my incomplete list by species (so far 23 of the 29 ACAP-listed species found, for some adjusted to reflect current taxonomy) by country/territory, with to me many surprising stamps depicting birds that if seen within the issuing country would be far outside their normal ranges, such as a Laysan Albatross in the waters of Tanzania, and a Short-tailed Albatross in land-locked Lesotho. So it's no use working out at-sea distributions from your letters!
Well out of its normal range?
A Buller's Albatross on a Moçambique postage stamp
Wandering Albatross Diomedea exulans: Antigua, Argentina, Australia, Comoros, Falkland Islands (Islas Malvinas)*, South Africa; South Georgia and the South Sandwich Islands (Islas Georgias del Sur y Islas Sandwich del Sur)*; Terres Australes et Antarctiques (France)
Southern Royal Albatross Diomedea epomophora: Aitutaki Cook Islands, Moçambique, New Zealand, St Kitts
Northern Royal Albatross Diomedea sanfordi: Republic of Guinea
Tristan Albatross Diomedea dabbenena: Tristan da Cunha
Amsterdam Albatross Diomedea amsterdamensis: Terres Australes et Antarctiques (France)
Black-footed Albatross Phoebastria nigripes: Grenada, USA
Laysan Albatross Phoebastria immutabilis: The Gambia, Tanzania
Short-tailed Albatross Phoebastria albatrus: The Gambia, Korea, Lesotho, Japan, Tanzania
Waved Albatross Phoebastria irrorata: Cambodia, Chad, Montserrat, USA
Atlantic Yellow-nosed Albatross Thalassarche chlororhynchos: Tristan da Cunha
Indian Yellow-nosed Albatross Thalassarche carteri: Terres Australes et Antarctiques (France)
Shy Albatross Thalassarche cauta: Comoros, Namibia, Samoa, Terres Australes et Antarctiques (France)
Grey-headed Albatross Thalassarche chrysostoma: Australian Antarctic Territory, Terres Australes et Antarctiques (France)
Black-browed Albatross Thalassarche melanophris: Aitutaki Cook Islands, Argentina, Christmas Island, Falkland Islands (Islas Malvinas)*, Ross Dependency (New Zealand), Terres Australes et Antarctiques (France)
Buller's Albatross Thalassarche bulleri: Moçambique
Chatham Albatross Thalassarche eremita: Guinea-Bissau, New Zealand
Sooty Albatross Phoebetria fusca: Tristan da Cunha
Light-mantled Sooty Albatross Phoebetria palpebrata: Argentina, South Africa, Terres Australes et Antarctiques (France)
Northern Giant Petrel Macronectes halli: Australian Antarctic Territory, Tristan da Cunha, Uruguay
Southern Giant Petrel Macronectes giganteus: Argentina, Falkland Islands (Islas Malvinas)*, Maldives, Ross Dependency (New Zealand; white phase), South Georgia and the South Sandwich Islands (Islas Georgias del Sur y Islas Sandwich del Sur)*, Terres Australes et Antarctiques (France), Tristan da Cunha
White-chinned Petrel Procellaria aequinoctialis: Falkland Islands/Islas Malvinas*, South Georgia and the South Sandwich Islands (Islas Georgias del Sur y Islas Sandwich del Sur)*; Terres Australes et Antarctiques (France)
Spectacled Petrel Procellaria conspicillata: Tristan da Cunha
Grey Petrel Procellaria cinerea: Terres Australes et Antarctiques (France)
It seems albatross stamps are more common than ones depicting ACAP-listed petrels. I have yet to find postage stamps for the two New Zealand-endemic Procellaria petrels, and stamps do not yet seem to have "caught up" with some of the recent albatross taxonomic splits (for example in the cauta group).
My personal choice of the best ACAP-species stamps: those from Tristan da Cunha.
Atlantic Yellow-nosed Albatrosses: an excellent example of philatelic art
John Cooper, ACAP Information Officer, 12 September 2011
*A dispute exists between the Governments of Argentina and the United Kingdom of Great Britain and Northern Ireland concerning sovereignty over the Falkland Islands (Islas Malvinas), South Georgia and the South Sandwich Islands (Islas Georgias del Sur y Islas Sandwich del Sur) and the surrounding maritime areas.