Yes, travel bugs do need to be quite sturdy. My Matilda Rabbit went around the world to Australia and back. She's a smallish porcelain Wade piece. She eventually made it home to a cache near me, but with the top of one ear missing, both ears broken off and araldited back in place, and one foot missing as well.
And as Mrs B says, make sure the TB tags are securely attached. I don't trust the little chains that come with the tags and I use strong cord instead.
Also, be sure to attach a mission statement to your ducks, preferably on laminated card or something similar.
Do not go gentle into that good night.
Rage, rage against the dying of the light. (Dylan Thomas)