Please let me know which zones you can find all the different feathers in!
Also, a large majority of these feathers (event or no) can be found inside elephant dung, so keep on digging!

All zones:
Archer's Buzzard Feather
Flamingo Feather
Shining Drongo Feather
Senegal Feather
Shoebill Feather
Kingfisher Feather
Vulturine Guinefowl Feather
Albino Feather (December only)
Nightjar Feather
Shrike Feather

Temperate Savannah:
Barn Owl Feather (Night only)
Hornbill Feather

Shrubland:
Grass Owl Feather

Tropical Forest:
Hornbill Feather (yes, again)

Dry Savannah:
Secretary Bird Feather

Rocky Hills:
Pel's Fishing Owl Feather
Grey Crowned Crane Feather
Cape Eagle Owl Feather
Striped Eagle Feather (Good Karma only)
Sacred Ibis Feather

Arid Desert:
Little Owl Feather
Sacred Ibis Feather

Marshlands:
Spoonbill Feather
Marsh Owl Feather (Night only)
Egyptian Goose Feather (Wet Season only)
Vulture Feather

Waterhole:
Crane Feather
Black Heron Feather (gives evil karma)
Long Eared Owl Feather

This is DEFINITELY not everything, not by a long shot. I collected everything I could from both memory or the wiki, but please comment if you see a feather not listed, and where you found it!