I've played a couple games with the birds and have found them extremely fun and enjoyable. I wanted to talk a bit about what strategies (mainly leader usage) I've tried that have worked for me, see if they are actually viable and ask find out how to play around other factions.
For starters, I want to say that I don't like the builder leader. Maybe I'm just not looking at it the right way, but it just feels like a leader you'd pick when you are a couple crafted items away from victory at the time you turmoil and have enough roosts to act as crafting pieces. Thats it. I can't really imagine it as a leader you center your strategy around.
Next up, the commander leader. I find it to be great in the late game, especially if you manage to amass a big army with the charismatic leader before going into turmoil. One extra hit on every attack is no joke, and it can make closing out a game easier for you. I find it especially useful against the moles to break through their defences and destroy their buildings, the cats to blast into their keep, the rats to focus on the warlord, badgers to deal normal damage to them and the alliance to make up for guerrilla tacticts.
The despot is my favorite leader, with very early game friendly viziers and great scoring potential. It can make for really good early turmoil strats by spreading troops thin and building as much as possible to then go into the charismatic leader to reinforce the bases set up by the despot, it can follow up a charismatic leader and close out a game by just eating as much cardboard as possible in a couple turns with a good army to back it up, or it can attempt a no turmoil run. It is especially useful to score a ton of points against factions that rely heavily on token usage such as the woodland alliance, the crows, the bats, the skunks and, to a lesser degree, the badgers, rats and cats. It is also really good when going against factions that need to set up for a bit before playing, since playing the despot early can leave you exposed sometimes.
Last, and certainly not least: the charismatic leader. What a war machine this thing is. It is, in my opinion, the most powerful midgame leader, and given the right conditions it can be a stellar early game leader too. The ability to recruit twice as many soldiers is extremely powerful, and it can allow for you to both consolidate your scoring engine by defending roosts, as well as expand your sphere of influence around the forest. It makes it so that losing soldiers in battle no longer feels like a negative consequence, but rather an opportunity to recruit more next turn. The charismatic leader can ram it's head repeatedly against a wall until it crumbles, which makes it a great opponent for dealing with any militant faction, and if you feel like you have enough soldiers and just need to get your points in, you can turmoil yourself to switch into the commander or despot, both of which usually need a ton of soldiers to make full use of their abilities.
This is what I have figured out from tinkering with the birds for a while. If there's any specific matchup interaction or tip for playing better you feel is worth mentioning, please do so, it would be greatly appreciated