Here is the full list of all 24 Kestrel achievements.
Buy the basic shot from the upgrades shop.
Defeat the boss in Learning.
Defeat the boss in No Shelter.
Defeat the boss in Turbulence.
Defeat the boss in Foraging.
Defeat the boss in Migration.
Defeat the boss in ...
Have more than 10,000 shards.
Have more than 100,000 shards.
Have more than 500,000 shards.
Destroy the pfeilstorch.
Leave the pfeilstorch behind.
Bring the pfeilstorch with you.
Destroy all the grass in No Shelter.
Collect every seed in Turbulence.
Destroy every bird in Migration.
Destroy every enemy in ...
Complete the game in under 45 minutes.
Find a warp back to the beginning.
Destroy the pfeilstorch twice.
Ignore the pfeilstorch completely.
Reach the credits.
There is another level.
Destroy 10 blocks on Foraging by colliding into them.