Parrots are able to mimic human speech due to their unique vocal anatomy. They have a specialized vocal organ called the syrinx, which allows them to produce a wide range of sounds and imitate human speech patterns. Additionally, parrots are highly intelligent and social creatures, which enables them to learn and mimic sounds from their environment, including human speech. With practice and exposure to human language, parrots can learn to imitate words and phrases with remarkable accuracy.