Installation:

Install Forge
Archive from folders BIRDS MOD [1.4.6] move in .minecraft / mods
Birds fill the void in sky.
Birds Mod (1.4.6) - Mods for minecraft

Craft:

BIRDS MOD [1.4.6]

Reference to the foreign source – minecraftforum.net/topic/1049762-146145144forge-birds-mod-beta-09/page__hl__146% 20mod__st__0

download mod