He has no special abilities, and is of average weight. This makes him usually the least useful bird for almost all situations.
Subverted in Red's Might Feathers, where the Mighty Eagle granted him special feathers that finally grants him a special ability. Said special ability involves dashing directly towards the pigs in the game.
Papa Wolf: He's very protective of the eggs, to the point of going berzerk over the slightest threat.
So are all of the other birds, but episodes like "Off Duty" and "Tooth Royal" illustrate that Red is the most serious about the eggs' safety, while the others would rather goof off unless the eggs are actually threatened.
Brilliant but Lazy/Crouching Moron, Hidden Badass: They usually spend their free time napping or goofing off, but can clear the obstacle course Chuck set up better than he could, and can beat down pigs as much as the adult birds when they have to.
Lady Not AppearingIn This Trailer: She never appears in any Angry Birds video trailer, and her only prominent appearance was in a Chinese cross promotion for Coca Cola and the summer Olympic games.
Lethal Chef: Her cooking can kill plants, but at least the pigs like it.
New-Age Retro Hippie: She doesn't look like one, but she holds the same values of pacifism and ecological harmony as stereotypical hippies, and her vision of the eggs in "Egg Sounds" are more blatantly obvious ones.
Technical Pacifist: She isn't as confrontational as the other Angry Birds, but she still fights the pigs when they try to steal the eggs.
Stone Wall: Her brute force would be ineffective, unless she drops an egg.
Team Mom: In the 'Meet the Flock' video for Angry Birds Toons, she is depicted as more obviously female and performs tasks like serving food to the other birds. Bonus points for being the tallest of the main five birds in the flock.
In the one trailer he has shown up in, he's portrayed as one in-universe, when he accidentally bumps into the slingshot, knocks a bird of course, and sheepishly tries to apologize to Red.
Crouching Moron, Hidden Badass: In the above-mentioned trailer. He's an eager and well-meaning Klutz who accidentally screws things up for the other birds, but in the end he singlehandedly saves the eggs from the pigs.
Lightning Bruiser: He travels faster if the direction of his flight path gets reversed.
Pokémon Speak: In the original game, if you listen closely enough, he will say "Angrrry.... Birrrd!" when fired from the slingshot.
Lightning Bruiser: Of the Pintsized Powerhouse variety. He's fast (somewhere between Red's normal speed and Chuck's fast speed), packs a surprising punch for his size (he can easily smash through wood and ice), and his ballooning ability can cause a lot of damage if used properly.
Perpetual Smiler: His default expression is a cheerful smile (or as close to one as a beak can get).
Art Evolution: Started off in the games with the same body type as all the other pigs (just larger), but has taken on a more plump, jowlier appearance in the comics and animated series, to hammer home his Fat Idiot traits.
Not-So-Harmless Villain: In the comic tie-in to Angry Birds Transformers he, as Lockdown Pig, takes a while adjusting to his form, ending up transforming into a toilet for issue one and part of issue two. He soon becomes useless to the pigs when he falls over and can on longer contribute. When he finds out how to Transform he easily overpowers Grimlock (who was taking on the other Deceptihogs and winning) and one-shots Bumblebee when the rest of the Autobirds show up.