I just used up 5 stacks of greens digging in Western Altepa Desert on a chocobo with both Burrow and Bore, but without Egg Helm. No Black Chocobo Feathers whatsoever. I'll try a bit more. And I may try with Egg Helm. I'll report back after. --Superguppie 12:53, December 19, 2009 (UTC)
Same setup in Konschtat Highlands, where Black Chocobo Feathers are also Uncommon finds. Got them fine there. I'll keep trying with different setups in different areas. Superguppie 12:29, January 16, 2010 (UTC)