Bird on Cage Floor
Cause
This may be the first sign of illness you see due to birds natural instinct to mask symptoms until they literally fall down. This is not an early sign, but a late and extremely dangerous one.
Treatment
Warmth is critical. Increase the temperature in the cage to about 90 degrees. A source of revitalizing solutions (see Revitalizing Solution section) is needed, administer 1/2 to 4cc depending on the size of the bird. Contact your Avian Veterinarian ASAP.