It has an extremely sharp sense of direction. It can unerringly return home to its nest, however far it may be removed from its familiar surroundings.
(From Bulbapedia) Pidgey is a small, plump-bodied avian Pokémon. It is primarily brown with a cream-colored face, underside, and flight feathers. On top of its head is a short crest of three tufts. The center crest feathers are brown and the outer two tufts are cream-colored. Just under its crest are its narrow, brown eyes. Angular black marking extend from behind its eyes down its cheeks. It has a short, stubby beak and feet with two toes in front and one in back. Both its beak and feet are a grayish-pink. It has a short, brown tail made of three feathers.
Pidgey has an extremely sharp sense of direction and homing instincts. It can locate its nest even when far removed from familiar surroundings. It is a docile Pokémon, and generally prefers to flee from its enemies rather than fight them. By flapping its wings rapidly, it can whip up dust clouds and create whirlwinds to protect itself and flush out potential prey. Gust and Feather Dance are its former signature moves. Pidgey is very common throughout its range and can often be seen in meadows and forests. Ekans is a natural predator of Pidgey.
(From Bulbapedia) Anatomically, Pidgey resembles a Cedar waxwing or House sparrow more than it does a pigeon. However, there have been some references to Pidgey Mail, alluding to homing pigeons. Its category, "tiny bird," added to the sound of the end of its name, could suggest that Pidgey is also based on a chickadee. However, it and its evolutions seem to have more traits related to ospreys than pigeons or chickadees.
(From Bulbapedia) Pidgey could be a corruption of pigeon or a combination of that with the word budgie (a type of bird), chickadee (a type of bird), or pudgy (referring to its plump physique).