My observations:
Goslings are much calmer than ducklings.
Ducklings are way more food driven.
Goslings do not mind being picked up and when I sit in their pen, they like to crawl up on me to go to sleep.
Goslings like to sit in their water bowls, but don't play with water the way ducklings do.
Goslings are more expressive and interact with me more... and they cry loudly when I leave the room.
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They also bite much harder and grow much faster. They are more inquisitive, and are like babies or puppies chewing on everything. Mine aren't very loud, unless they've made a mess and need more water. If they hear me talking then, they will talk back until I come see what they need.