Special Unlockables - These are obtained by doing certain things in Single Player Campaign.

Blanka Ball Get a perfect abduction on all Single Player levels
Chicken Trophy Get at least a Bronze Medal on all Single Player levels
Cow Trophy Get at least a Gold Medal on all Single Player levels
Infinite Boost Get at least a Gold Medal on all Single Player levels
Pig Trophy Get at least a Silver Medal on all Single Player levels
Sheep Trophy Get a perfect abduction on all Single Player levels

Unlockables

Bowled Over (Silver) Kill 10 chickens with one throw of a boulder - strike!
Defender of the Flock (Silver) Complete a level featuring the night-time predator without letting it eat any animals
Don't Fence Me In (Bronze) Knock over 50 fences with a cow (Aggregate Total)
Fertilizer (Bronze) Make 50 Piles of Poo (Aggregate Total)
First Flock! (Bronze) Completed First Level
Good Shepherd (Bronze) Flock 25 Animals at Once
King of the Skies (Bronze) Fly and Land 75 Chickens (Aggregate Total)
Love Bunny (Silver) Use 3 Love Patches in 3 Minutes
Lumberjack The Ripper (Bronze) Rip Up 50 Trees (Aggregate Total)
Make Your Mark (Bronze) Complete 10 Crop Circles (Aggregate Total)
Master Flocker (Gold) Get a perfect abduction on all levels, singleplayer and multiplayer
The Continuous Cartographer (Bronze) Play through one user-created singleplayer level and one user-created multiplayer level
Unidentified Flocking Object (Bronze) Abduct 20 Animals (Aggregate Total)