Some pigs have a passive ability, and depending on this ability it will either deal bonus damage to your opponent, heal your team or reduce your Super shot counters when knocked out. Every pig has a symbol above its head displaying the passive ability.

Extra Damage  - These pigs will deal extra damage to your opponent's team when knocked out.

Super Shot Reduction - Reduces Super Shot Counters for all birds of the player who defeated the pig.

Health Boost - Heals the birds of the player who defeated the pig.

You can also check the pigs' abilities by tapping them.