Complex sentence: Alcids are superficially similar to penguins due to their black-and-white colours, their upright posture and some of their habits, however they are only distantly related to the penguins and are able to fly.
Split into simpler sentences: Alcids are superficially similar to penguins due to their black-and-white colours, their upright posture, and some of their habits. However they are only distantly related to the penguins and are able to fly.