Minecraft wiki entry for Development_versions, associated text: Sheep now spawn in meadows.
Rabbits now spawn more frequently in meadows.
Donkeys now spawn less frequently in meadows.
Blue orchid no longer spawns in meadows.
Meadows sometimes spawn a lone oak or birch, often with a bee nest.
Hostile mobs now spawn in the new mountain biomes.
Infested stone now generate in the new mountain biomes.