The nests are built of interlocked sticks, often thorny, assembled into a mass in a tree crown or on a pylon, palm or transmission tower. Each pair maintains its own chamber with its own entrance, and a large structure may hold many chambers. Because the birds add material continuously, established nests grow substantially and can reach the weight of a small vehicle.
The nest is used year-round rather than only for breeding, providing a roost through winter, which is one reason feral populations survive in climates far colder than the species' native range. Chambers also buffer temperature.
The same habit creates the conflict. Nests built on electrical infrastructure cause faults and fires, and utilities remove them at cost. Several jurisdictions restrict keeping or releasing the species for that reason. Whether feral monk parakeets significantly damage crops outside South America is less clear than the electrical problem, and evidence for major agricultural harm in introduced ranges is thin.