Unfezant differ in appearance depending on their gender; male Unfezant are very colorful with a green belly and pink ribbon-like feathers protruding from their heads, but female Unfezant
are colored brown. However, they both have great attack stats and good speed. This gender difference is based on real birds, since the males are almost always more colorful than females.
The Gym Leader Skyla uses a Level 33 female Unfezant in her party.
Cheren uses a male Unfezant at Level 65 when it was last seen on Victory Road.
Unfezant is the evolved form of Tranquill starting at level 32, and the final evolution of Pidove, evolving into Tranquill at level 21.
Its gender difference is apparently similar to real birds; The male usually being more colorful so it can catch the attention of a female, who is not as colorful as the male. In real life this is called a crest.
The English name 'Unfezant" is taken from the pheasant, the bird that it is most likely based on. It is also a parody of "unpleasant," because Unfezants do not bond with anyone but its trainer.
Though Unfezant is based on a pheasant (hence part of its name), its first forms, Pidove and Tranquill, are based upon pigeons.
The heart-shaped lighter patch of feathers that was on Pidove's breast is now over Unfezant's face.
Its first forms, Pidove and Tranquill, have no gender differences, although Unfezant does (the Male has the pink stripes on its head, but the Female does not).
In the anime, Unfezant's Pokedex entry states that the flying capabilities of the female Unfezant exceed that of the male. This could be something that really does apply in the game, or this could be an Anime-exclusive fact that was made up to either give Ash's Unfezant a better chance against Skyla's Swanna, or just to make Ash's Pokémon look better despite the misconception of certain fans that female Pokémon are inferior.