Here is the full list of all 20 Dune Sea achievements.
Get 6 Flock Birds
Collect 10 Gold Flowers
Dive Through a Cloud
Collect 20 Fruits
Roll + 2 Honks after Dive
Roll + Honk after Puzzle Solve
Passed the First Puzzle
Crash into ground 10 times
Collect a flock bird
Beat the First Chapter
Fly back 100 meters
Bump into rocks 5 times
Collect 150 Seeds
Scrape 5 rocks
Land on a Platform
Complete First Checkpoint
Make a Turn and Back
Airbourne for 50 meters
Glide for 50m
Pass 4 Checkpoints in a row