Complex sentence: The takahē is monogamous (with pairs remaining from 12 years to, probably, their entire lives), builds a bulky nest under bushes and scrub, and lays one to three buff eggs.
Split into simpler sentences: The takahē is monogamous, with pairs remaining together from 12 years to, probably, their entire lives. It builds a bulky nest under bushes and scrub, and lays one to three buff eggs.