The Diablo 2 Wiki
The Diablo 2 Wiki archive is available for anyone looking for information on Diablo 2. All information here is pre-D2R but contains a lot of useful information that is still relevant. Updated sections for new D2R features can be found on the PureDiablo Diablo 2 section

Chickens

From Diablo 2 Wiki
Npc-chicken3.jpg

Numerous chickens can be seen roaming the Rogue Encampment, and presumably serving as food, as at least one of the bunnies does in Harrogath.

The chickens are not just moving decorations though, like the various human NPCs seen in each town in the game. The chickens actually move, flapping their wings and running a few steps when any character walks over one. This amusing AI can be turned into a game, and during the closing days of the Diablo II Open Beta, bored players started herding chickens out of town and into the wilderness, where the monsters occasionally took a liking to them.

Chickens can be driven as far as the Stony Field, in the final game, but no further, since they can not descend the steps into the Underground Passage.

Chickens can be herded out of town.