In its native habitat Red-masked Parakeet has been encountered in pairs or small flocks of up to 12 away from and up to approximately 200 individuals at communal evening roosts (Best et al. 1993, 1995). Naturalized populations in California (Mabb, personal communication, Bittner 2009), Hawai'i (Kalodimos, personal observation) and Florida (Pranty and Garrett 2003) number between an estimated 50 and 300 birds and each of these entire populations communally evening roosts together. California and Florida populations nest in tree cavities - usually one pair to a tree with nesting trees used distributed across the landscape (not clumped), whereas in Hawai'i, populations nest colonially in inland rock cliffs. In San Francisco, CA, USA the first few Red-masked Parakeets were seen in 1987 and as of 2009 the population had reached an estimated 200 birds (Bittner 2009). On O'ahu, Hawai'i, Red-masked Parakeets were first documented in 1985 and since then the population has grown to a high of 65 individuals. Systematic evening roost counts by the author, using recorded images, show that the population has decreased to between 50 and 60 individuals. In these naturalized populations all members evening roost together in the same location each night. The evening roost locations in California USA and O'ahu, Hawai'i have been large trees. When disturbed from its evening roost in O'ahu, Hawai'i, the population used a number of temporary alternate evening roosts for about three months, after which time the entire population returned to the original main evening roost. If more than one alternate roost was used only a portion of the population would use each of them, but these separately-roosting flocks would join up during the day. All evening roosts chosen (including the traditional one) were near the coast (even though birds spent much time in inland valleys during the day). In general, without roost disturbances, in Hawai'i, this species appears to evening roost in the same locations for its entire lifespan. Distances traveled by San Francisco, CA, USA population members are recorded as being up to 12 km, but more commonly between 2 and 5 km, from the evening roost (Bittner 2004) and up to 6 km from the evening roost in Hawai'i.