Well I will put them in order of Least to Greatest.
Pidgeot pretty much fails at life it only has good speed and Ok Attack, a pathetic movepool that makes even Flareon laugh at it, and his best set is probably a choice-specs one so he can use Heat-wave to cover Steel types.
Unfezant, while it has a pretty good attack stat and decent NU defense it will be destroyed by special attacks and really its main function is sweeping and Wish passing. It can run some unexpected sets with Hypnosis, Taunt, and Wish, but is otherwise pretty much useless.
Noctowl is not too bad in NU he has some nice tools, his main downfall is that base 50 Defense. He is definitely a special wall/tank. I use him as a Toxic-staller with Night-shade for attacking and Roost for healing. He can be pretty good if used correctly but he does not exactly strike fear into the hearts of his Foes.
He also has the same eyebrows as Headmaster Gaepora from Skyward Sword.
Fearow seems a lot like Pidgeot at first glance, just with lower bulk and more Speed and Attack and no Brave-bird. So why is he so much better? Well he has Drill-peck which is while weaker than Brave-bird it does not have recoil. Is that the reason? No, the reason is HE HAS A GROUND TYPE MOVE! Drill-run! Probably the only Pokemon that can learn it that makes good use of it(as Rhyperior and Excadrill already have Earthquake) this move covers Rock weakness and Steel-resistance. Use him as a pure sweeper.
Swellow is our first step out of NU into RU my personal favorite bird can be powerful if used correctly. Guts+Flame-orb gives this guy a great Attack stat combined with that super high 120 base speed stat he is a great sweeper. Though he fears Choice-scarfed Pokemon, priority, and sashes.
The highest tier of these kinds of birds(UU I think) Staraptor has a high Speed and great Attack, and he has something that none of the other birds has Close-combat! This move covers Rock and Ice-weaknesses that other birds are forced to cover with Steel-wing but Staraptor gets the stronger and more accurate Close-combat which also allows him to hurt Steel types as well.
