Unlike Pidgey, Spearow has a terrible attitude. It is very wild and will sometimes attack other Pokémon and humans.
– Ash’s Pokedex
Spearow is the other early Normal bird Pokemon in Gen I. I’m not sure why it exists, because in subsequent generations, there is only one family of early Normal birds… I’m not sure if it’s supposed to be a counterpart to Pidgey like Caterpie and Weedle families, because while Pidgey’s family has 3, Spearow only has two.
Spearow appeared early in the anime; a flock of them attacked Ash in the first episode, and through defeating the flock, Pikachu and Ash became friends.
The highest stats Spearow has are in Speed and Attack. Even though it’s tiny (1 foot tall), like Pidgey, it can learn Fly and can fly its trainer around somehow.