Here is the full list of all 29 Rocketbirds: Hardboiled Chicken achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Complete the Cooperative game mode
Kill 300 penguins or clones
Punch or kick 100 times
Kill 100 penguins or clones
Kill 10 enemies, each with one gunshot
Kill an enemy by knocking him into a laser door
Overthrow Putzki and liberate Albatropolis
Find 3 Signs
Find 20 Signs
Find all 45 Signs
Juggle an enemy for 10 seconds
Kill a helicopter penguin with his own missile
Kill 6 helicopter penguins with their own missiles
Escape the large zeppelin with 40 seconds or more on the timer
Kill 30 Penguins as they step out of a door
Brainbug 30 enemies
Brainbug the penguin above the star in Chapter 6 (Single Player)
Kill 20 enemies while brainbugging
Brainbug at least one penguin from each of the 7 penguin ranks, including Putzki
Kill Brno with the knife
Kill 2 enemies with one grenade
Kill 3 enemies with one grenade
Kill 6 enemies with the bazooka
Carry the other cooperative player for 500 meters in the same chapter without dying
Launch the silo missile
Stack all 3 crates near the end of Chapter 11 (Single Player)
Kill all penguins stationed on the zeppelin in Chapter 3 (Single Player)
Kill all penguins stationed on the small zeppelin in Chapter 8 (Single Player)
Kill all penguins stationed on the big zeppelin in Chapter 8 (Single Player)