Describe the bug
Ducks despawn from the world when left in unloaded chunks unless nametagged. The duck sack doesn't give them permanence, nor does breeding them or hatching them from an egg. Geese work fine, this is only a duck problem.

To Reproduce
Steps to reproduce the behavior:

1. Spawn a Duck, or find one in the world
2. Fly/Run away to unload the chunks with the Ducks for a minute or two.
3. Return to where the ducks were.
4. See error

Expected behavior
Ducks would remain in the unloaded chunks like chickens or geese.

Version
0.2.1 Forge