What is the difference between Congo and timneh African grey parrots?

Congos and Timnehs are two widely recognized subspecies of the African Grey Parrot. The main differences are size and coloring, although this can vary. Timnehs are smaller, darker-feathered, have a darker tail, a pale upper mandible (almost pink), and a greyer eye. There is no difference in talking potential, although larger birds may have deeper voices. Many people have noted that Timnehs seem a bit less prone to nervous behaviors like feather-plucking. Congos are more often cited as exemplars of good talking and intelligence because they have been more popular and more well-studied. Their greater popularity seems to be based on their size, some people think bigger is better. Timnehs are quickly gaining in popularity. Their smaller size and reputation make them very attractive companion birds.