From Glitch City Laboratories
(Redirected from Bird Type
In addition to the standard fifteen Pokémon types of Pokémon Red, Blue, and Yellow, and the seventeen types in Gold, Silver, and Crystal, there is another type hidden in the programming. This type is called BIRD.
The BIRD type is quite enigmatic. Its attacks are physical, or would be if any existed. No attack is of the BIRD type and no Pokémon is of the BIRD type. There are no types super-effective or not very effective against it, nor are any types weak or resistant to it.
Interestingly enough, MissingNo. and 'M are partly BIRD type. However, 'Bird' never comes into play outside of Pokémon glitches.
This type was never removed from the source code, and exists in all games up to and including Pokémon Crystal.
Many believe that Bird was the original name for the Flying type.