Rockslide Tusk has been my answer for a lot of deeply annoying things in this game. Removes the birds, Now the spider, and makes your match up into the stupid ice dragon better if you prefer headlong over CC. Too bad that there's still no fucking Rockmove that isn't 100 accuracy that is readily applicable.
Rock Slide doesn't actually remove any of the birds aside from Moltres due to the low Base Power.
252 Atk Great Tusk Rock Slide vs. 248 HP / 244+ Def Zapdos: 134-158 (34.9 - 41.2%) -- guaranteed 3HKO
You'd need roughly 31% chip to 2HKO Zapdos, not to mention that it can still miss, and Rock Slide obviously tickles something like Corviknight.
252 Atk Great Tusk Rock Slide vs. 0 HP / 0 Def Kyurem: 180-214 (46 - 54.7%) -- 58.2% chance to 2HKO
And against Kyurem, it's not even a guaranteed 2HKO, so if you chunk it once, it could still survive if you switch out and hit it with Rock Slide again when it comes in.
Usually, I believe more accurate moves are better than less accurate moves, but with a 25 Base Power difference between Stone Edge and Rock Slide and only a 10% increase in accuracy, I believe Rock Slide tends to not be worth it unless you get STAB on it, some other power multiplier like Sand Force for Excadrill in Gen 5, or have Swords Dance.
252 Atk Great Tusk Stone Edge vs. 248 HP / 244+ Def Zapdos: 178-210 (46.4 - 54.8%) -- 59% chance to 2HKO
For reference, Stone Edge can 2HKO Zapdos, whereas Rock Slide never does.