Pidgeot's evolutionary chain is a three tier chain with Pidgeot being the final tier. Its begins with Pidgey and then once it reaches level 18 it will evolve into a Pidgeotto. When Pidgeotto reaches level 36 it will evolve into a Pidgeot. If given a Pidgeotite as its hold item it can evolve once again, using a new evolutionary technique called Mega Evolution Pidgeot can Mega Evolve into Mega Pidgeot.
Introduced in Pokémon X/Y for the Nintendo 3DS, Mega Evolution is a new evolution method giving Pokémon battles a whole new twist. With the use of a Mega Ring/Bracelet, a high friendship, and the appropriate battle stone the Pokémon gains access to a new form and can gain higher stats, new abilities and even a change to its type! However, unlike normal evolution Mega Evolution is not permanent and the Pokémon will revert back to its normal form once the battle has ended. There are also some limitations too as only one Pokémon can Mega Evolve per battle, and not every Pokémon can Mega Evolve. Boooo!
While Pidgeot does not have a Mega Evolution form in Pokémon X/Y it does in Pokémon Omega Ruby/Alpha Sapphire. In order to Mega Evolve Pidgeot you will need to find a Pidgeotite. To get this item you must first help a girl in Verdanturf Town find her Shroomish, which is hiding behind the big sign. In doing so she will give you an Intriguing Stone. If brought to Mr. Stone in Rustboro City he will tell you that it is a Pidgeotite and then give it back to you. I must say it is completely badass. Aside from a totally awesome look, Mega Pidgeot gains a slight buff to its Defense and Special Defense stats, a modest buff to its Speed, and a huge buff to its Special Attack. Suddenly those Special Attack moves are looking more appealing. Mega Pidgeot's type is still Normal/Flying.
Mega Pidgeot also gains the Ability No Guard, which in battle assures any attack done by or to the Pokémon will hit. Even if the Pokémon uses moves that provide immunities like Protect or Detect, or moves that make the Pokémon semi-invulnerable, like Fly or Bounce, it will still take damage. However, attacks against full immunity moves will fail if the Pokémon uses always hitting moves like Swift and Aerial Ace and will still be blocked. To improve chances of breaking through, lower accuracy attacks, like Hurricane and Steel Wing, are better to use. It definitely makes things more interesting if nothing else.