Complex sentence: Parrots in captivity may suffer from boredom, which can lead to stereotypic behaviour patterns, such as feather plucking, which is likely to stem from psychological rather than physical causes.
Split into simpler sentences: Parrots in captivity may suffer from boredom, which can lead to stereotypic behaviour patterns, such as feather-plucking. Feather plucking is likely to stem from psychological rather than physical causes.