Ravens make terrible zombies. They lose weapon finesse, and gain none of the usual zombie bonuses to AC and Slam attack from size, so their attacks are pitiful. They lose their ranks in Fly and have their fly rank dropped to Clumsy, so it takes them quite a while just to turn around.
Their saving grace is that they're damn near impossible to kill, and can swarm for huge fire damage. (4 Tiny creatures can share a space, and anything within 5 feet takes damage from their aura, so these guys can land all around a medium creature and deal 26d6 fire damage at the start of that creatures turn)
Edit: On reflection, this seems a little silly on both ends. To tiny attack, and way too big aura damage. Their stats as they stand make them into reusable missiles more than anything else. I'm going to try to think of something to fix this.
Like corn in a kettle, one by one the birds eyeballs burst, boiled from within. They were replaced with cherry red embers set deep in their skulls. Their bodies smoldered, but never quite seemed to catch. The effect was something like looking at a blackened log in a fire that was beginning to burn out, the glowing embers rippling along the veins of the soot-black feathers.
They flapped their wings and cawed, a rasping, awful noise like a bird choking on smoke. Fires flared up along the edges of their wings as the air churned from their flapping rushed through the smoldering feathers.
Their beaks dripped with boiling blood that hissed and spattered where it fell, blackening almost instantly and filling the the air around them with the pleasant scent of cooked bird.
They exploded forth from the tower, leaving it a burning ruin, screaming out their hate and circling round, each leaving a black trail of smoke behind it.
The sky above Ballentyne became the broken spiral.