In the PvP arena you are matched against players and compete with them for a gem reward. You have one week to collect as many stars as possible to be promoted to a higher league. Top three players are promoted to a higher league when the week ends, while bottom three players are demoted to a lower league. Make sure to collect at least some stars each week so that you don’t get demoted!
The Legendary League, however, works a bit different. As this is the most competitive league of them all, you need to be among the best of the best not to be demoted.
The score in the arena depends on the level of the birds; the higher the level the more points you'll get. You can level up your birds by finding feathers; you'll notice that it is easier to compete against others once you have higher level birds. You can see the level of your birds and how many feathers are needed to raise their levels in the nest.
In the Arena, you can get a winning streak by winning consecutive battles. Each position in the win streak grants better and better prizes, up to a streak of 7 wins! In the Legendary league, however, the streak goes up to 10!
Losing a battle will break the win streak, and you'll start over at the first position with your next win. After completing an entire win streak of 7 wins (10 in the Legendary League), you will start over with a new streak to complete.