Eastern Cobalt Plateaus - 7

Strategy
Choose Red in Guardian, Matilda in Druid and Bomb in Cannoneer/The Blues in Spies. Heal with Matilda if the birds' health isn't full and if their health is full, attack with her. Then attack with the others (Focus on Desert Pig (Boss) first, then attack the others or attack the others first, then the boss). Also, remember to protect the birds with Red before you attack to lower Desert Pig's strong attack. Use the Rage Chili on Red (if you want to smash the boss), on Matilda (if you want to heal your birds. This is perfect in case of emergency) or on Bomb (if you want to deal serious damage to all pigs at once) when it is full. Remember that if you choose The Blues, use their secondary skill in case of emergency. Repeat this over until you win or either lose.

Another strategy
Shown in the video below.