Here is the full list of all 39 Leave The Nest achievements.
Fly through 10 windows
Get a 50X multiplier
Fly through 15 zones
Fly for 5 minutes
Fly through 10 zones
Unlock Spoopy the spooky bat
Unlock Billy the bold bluejay
Unlock Henry the hyper hummingbird
Unlock Olly the observant owl
Unlock Gully the seagull with no equal
Unlock Touky the tough toucan
Collect 100 coins
Fly with the train for 10 seconds
Fly with the train for 5 seconds
Unlock Cardy the charismatic cardinal
Unlock Corey the caw caw crazy crow
Get a 15X multiplier
Unlock Manny the mallard with valor
Fly through 5 zones
Unlock Polly the pirate parrot
Dive for 2 seconds
Unlock Philly the fastest falcon
Collect 50 coins
Get a 5X multiplier
Unlock Elly the energetic eagle
Collect 10 coins
Fly above the clouds for 8 seconds
Unlock Sally swan the swift skimmer
Unlock Finny the finch who doesn't flinch
Unlock Firdy the fast bird
Fly for a minute
Fly above the clouds for 5 seconds
Fly above the clouds for 2 seconds
Touch the sky
Fly through 50 windows
Fly through 25 windows
Fly for 10 minutes
Visit every zone in one flight