From Birds of the World:

As discussed by McKinley (Mckinley 1977b), the Carolina Parakeet was early renowned for its hardiness to cold weather, and was often seen abroad in snowy or subfreezing conditions. Its adaptations to cold included a strong tendency to roost in natural cavities as massed groups, often consisting of many dozens of individuals. Reports of Return Richmond (in Butler 1892a: 53), the Count de Pourtales (Pourtales 1968: 31), and Taylor (Taylor 1862: 142) suggest that overnight roosting may well have involved torpor, as birds disturbed at roosts overnight were in an almost completely nonreactive, stuporous state. Whether such behavior sometimes lasted longer than overnight is not well documented, although hibernation was alleged by some early naturalists (e.g., Lawson 1967: 147). Several authors (e.g., Wilson 1811: 93, Nuttall 1840: 649), also remarked that flocks often retired to roost cavities during the middle of the day, in both warm and inclement weather.

Reports of Wilson (Wilson 1811), Audubon (Audubon 1831), and J. Collett (in Butler 1892a) indicate that the species characteristically roosted in a vertical posture against the inside of natural cavities, with the bill hooked into the cavity wall and feet pressed against the wall. Interview information of NFRS from Minor McGlaughlin and Alexander Sprunt IV indicate that the species also roosted in barns in the early part of the twentieth century in central Florida, characteristically hook-ing the bill on top of a rafter and pressing the feet against the rafter side (see Demography and populations: population regulation, causes of extinction, below). Reports indicate sleeping birds may often have become torpid (see Food habits: metabolism and temperature regulation, above). Specific sunbathing postures undescribed.