Harry's Mad by Dick King-Smith. Ages 7+.
Harry's Mad (1984) by Dick King-Smith tells the story of Harry Holdsworth and his unexpected inheritance: Madison, an African Grey parrot from America who can hold intelligent conversations. Mad, as Harry calls him, is extraordinary — highly intelligent, witty and opinionated. He becomes Harry's best friend.
When Mad is stolen by thieves who don't realise what they have, Harry is devastated. Mad's own intelligence eventually helps him escape his captors and find his way home — in an adventurous and funny journey that makes clear just how remarkable he is.