Serve your birds bean mixes and ready-made bird breads. A good diet helps the bird resist infection and they are stronger and healthier. You must take care of a bird's wings and feet. Keep the toenails cut. If you cut too close use a quick stop pencil, or a special avian powder for stopping bleeding or if nothing else is available, regular kitchen flour.
Cockatiels are very strong flyers.
You must trim their wings. Even trimming their wings only slows them down. When clipping the wings be careful to watch for new growth, or blood feathers. If you do cut one, the remaining part of the feather will act as a straw and siphon blood. This can cause them to bleed to death.