Complex sentence: It breeds in river valleys and rugged wooded mountain ridges between 1000--4000 m (3,300--13,200 ft) altitude where it nests in colonies beneath overhangs on vertical cliffs, laying three or four white eggs in an enclosed mud nest.
Split into simpler sentences: It breeds in river valleys and rugged wooded mountain ridges between 1000--4000 m (3,300--13,200 ft) altitude. It nests in colonies beneath overhangs on vertical cliffs, laying three or four white eggs in an enclosed mud nest.