The colony builds a shared thatched roof of coarse sticks with chambers entered from below through downward-facing tunnels. Chamber entrances are often lined with sharp spikes of straw that impede snakes. A large structure can hold over a hundred chambers and weigh enough to break the branches or utility poles supporting it, which is a real cause of colony loss.
The mass of vegetation buffers temperature. Interior chambers stay markedly warmer than the outside air on cold desert nights and cooler than ambient during the day, which reduces the energy an individual must spend on thermoregulation in a climate with wide daily swings. Birds roost in the chambers year-round, not only when breeding.
Because the structure is maintained rather than rebuilt, occupancy can far outlast any individual bird. Estimates of a century of continuous use for the oldest colonies are widely reported, though precise ages are hard to verify because dating relies on inference rather than direct record.