No bird should be raced except when in the most perfect physical condition. Such a bird invariably has a CLEAR WHITE WATTLE and CERE about the eye. The EYE itself should SPARKLE WITH LIFE AND STRENGTH. The feathers ought to FIT CLOSELY to the pigeon's trim body and possess an EXQUISITE PURE SHEEN. The FEET of healthy birds are always a DEEP RED. Male birds when in prime condition DO MUCH COOING AND CROWING. They also FLAP THEIR WINGS as if conscious of their strength for long and sustained flights.
Taken from Young Bird Training Methods
by Chas. Heitzman
Charlie also goes on to say, The trained ear can hear which pigeons are in form by listening to the different tones and sounds of the circling birds.