In its native habitat Red-masked Parakeet is encountered in pairs or small flocks of up to 12 individuals during the day, and in flocks of up to approximately 200 individuals at communal evening roosts. A. erythrogenys presence/absence pattern in certain areas is reported to be seasonal, which probably is probably connected with food availability or the nesting season (Best et al. 1993, 1995, Chavez-Riva 1994). Marchant (1958) states that "on the Santa Elena Penninsula, south western Ecuador, non-breeding flocks were present from April through August 1957" and then absent for the remaining calendar months. Nesting parakeets are absent from traditional nesting locations outside of the nesting season (Chavez-Riva 1994). The absolute number of A. erythrogenys making flights between nesting and foraging locations (e.g., into and out of a valley) was positively correlated with the number of active nests (Chavez-Riva 1994).
The San Francisco, California population of Red-masked Parakeet, of approximately 200 individuals, roosts together as one population in the same urban location where the founding individuals were seen in 1987. Sub-flocks forage in the suburban areas between two and five km from this roost location and one sub flock up was seen 12 km from this evening roost area (Bittner 2004).
In Hawai'i a radio telemetry study conducted by the author on a population of approximately 55 to 60 Red-masked parakeets showed that they have daily maximum movement distances to foraging and nesting locations of about six km from the coastal communal evening roost. A. erythrogenys practiced a bimodal daily activity pattern: a typical day would involve the population synchronously departing the evening roost at sunrise and dividing into two flocks that went to different locations. These subflocks, in their respective locations, socialized and conducted maintainance behaviors in routine congregation trees until about 7:30-8:00 after which they would depart to forage in groups of 2 to 25 in nearby food trees, usually Cordia sebestena and/or Prosopis pallida. After foraging they socialized e.g., individuals chased each other, investigated cliff crags, courted, allopreened each other, etc. Following this active period, at about 11:00-14:00, small flocks quietly rested usually in pairs or trios in the dense canopies of Monkeypod, Samanea saman, or Mango, Mangifera indica, trees nearby their morning activity areas. At 14:30-15:00 the flocks headed off to foraging locations, often the same morning foraging locations, until about 16:00; by 17:00-17:30 they would depart to the vicinity of the evening roost where more socializing took place. Variations to this general pattern occurred in relation to the nesting cycle.
Population members would spend more time in the vicinity of nesting cliff sites in between April-June after which time non-nesting A. erythrogenys would stay away from the nesting cliff site.
In flight, breeding pairs generally flew closer to one another but flock order was very loose with birds shifting positions resulting in a constantly changing flock shape. Pairs were readily identified while perched as they always stayed close to one another and frequently allopreened each other. Agonistic interactions during flock foraging were minimal. Individuals, even mated pairs, usually fed spaced apart within a tree, and when in close contact more dominant flock members (always older) would grab harvested food from other bird's bills, though this was not a common occurrance. Foraging birds usually departed food trees synchronously as a flock. Afternoon and evening-sleeping pairs would allopreen and sleep next to one another. Their most recent offspring would also sleep clumped among themselves but spearated from their parents.