My specialty comparisons
Pidgeot the orignal bird is one of the few pokemon that knows feather dance. Pidgeot's best stats are speed and attack.
Fearow the second bird of the bunch has high attack and speed. drill peck and return make this pokemon dangerous.
Swellow is one of the fastest pokemon ever having the speed stat of 125! swellow also has a decent attack stat and return.
Starapter the best of the bunch has the second highest speed of the four tied with fearow and amazing attack on pair with weavile. return is a great move it also has brave bird to make it super strong. and it is the only one that does not have to rely on steel wing to protect against rock and ice types becuase of close combat.
Pidgeot has sadly average every thing it doesn't even have remarkable speed only 91. It also has a bad move poo(move poo is a bad move pool so this bird has a rancid move pool).
Fearow though better than pidgeot in the signiture stats and has drill peck it has frail defenses so even with roost jolteon(the enemy of birds ever where) can easily OHKO it.
Swellow though has amazing speed has only ok attack and a shallow movepool. And even with that great speed jolteon can still outrun it and kill with thunderbolt becuase it to has frail defenses.
Staraptor though the best of the bunch the bunch wasn't to good to start with. Staraptor's defenses are as bad as the others. It has a better move poo but it is still a move poo.
So starapter is the best