Okay, this is mostly for fun, but if you have a flying animal who needs to suddenly launch themselves in the air with a spring mechanism, why not?
The Archery bird's beak is long, stiff, and it can dislocate it's lower beak, then lock it back into place sideways using great force applied by small wing hooks. additionally, the beak has a long tendon it periodically regrows that attaches to the ends of the beak. This tendon is snapped taut when the beak is in it's sideways position.
The need for the bird to get airborne in dense foliage means it can't just flap wings - it would hit vegetation. climbing, for some reason, is risky. Maybe poison predators, or carnivorous plants. So the archery bird strips down a small tree or bush, hooks it's tendon over the top, and uses it's wing hooks to pull down on the taut tendon. when enough tension is applied, the bird fires itself upwards like an arrow from a compound bow.
If you care to be REALLY creative, the bird can also use a gland that exudes glue to attach it's own feathers to sticks either sharpened or tipped with a special piece of eggshell. It's a living bow. So the bird has a hunting behavior it can use from high perches to strike prey at a distance and avoid whatever nastiness makes it unwilling to climb up trees. It flies to the ground, swallows the best parts of the prey, then strips a tree and launches itself back into the sky.