Snuffy, I think you may be mistaken:
Four feathers on the thrush (the one that lost the other 39,996)?

That would make for a total of 40,000. Surely the expression is 33,333 feathers on a thrush's throat. Hence the bigo call of "Fevvers, 33"

Cheers
Nigel
(Missing Misking, so getting a dose of Mudcat!)