Behavior patterns associated with pairing, precopulatory, copulatory and postcopulatory activities in Melopsittacus undulatus (a colonial psittacine parrot) are described ; and their possible function, causation and evolution is discussed. Heterosexual pair formation involves 3 obvious activities; Head Shaking, male Loud Warble and female following of the male. Two of these are also seen in precopulatory context. Courtship feeding, reciprocal preening and possibly Loud Warbling or other vocalizations, sidling activities, Courtship feeding, Head-bobbing and attempts to mount. tions variously in precopulatory stimulation and providing nourishment to an incubating or brooding female. Its role as a possible "reward" or appeasement to the female during precopulatory behavior is discussed. Typical male precopulatory behavior consists of 6 "Nudging-Pumping actions", various vocalizations, sidling activities, courtship feeding, Head-bobbing and attempts to mount. Redirected precopulatory behavior and Head Shaking (possibly derived from displacement head shaking) are quite common and redirected aggression is less so. These are described and causally and functionally discussed. The manner of copulation is unique. The male generally plays the more active role in courtship with a typical conflict of FaM (sensu MORRIS, 1956a), while the female shows a typical conflict of fAm. The importance of crown and throat feather adjustments, typically sleeked or normal in the female and ruffled in the male, as possibly signalling the relative motivational states of both sexes is discussed. Also, the ruffled male crown and throat feathers may serve as appeasement towards the female.