Silver gliders can take damage when you land if you have enough of the jump boost effect applied

1. Give yourself jump boost
2. Pick up a silver glider
3. Jump
   Only happens if the player has jump boost and the dragon does not.

They take fall damage if the player does, all entities that ride others that take fall damage take the same damage. This is considered a MOJANG FEATURE, don't ask me why, but its intentional.