Small Bird is a useful early to mid game creature with the relatively unique ability to ignore the taunt effect of a card. It will also gain Haste if there's already a monster (either ally or enemy) with Taunt or Armor on the board.
This makes it particularly useful against decks such as Patience which rely heavily on taunts. Similarly it's useful in Patience in conjunction with Snow Storm when wishing to deal damage whilst the board can have taunts. It's also decent in Bravery when you wish to quickly deal damage but are blocked by taunts.