1) For growth
2) For maintenance and performance
3) For renewal of the feathers
4) For reproduction
And finally, if it is really good enough, the parent bird will even use it to feed her chicks!
Katrina choosing to feed her chicks with the moistened dry food instead of the crickets.
Katrina holding a lump of moistened dry food between the beaks and encouraging her chicks to pick up the food on their own, from the cage floor.