Kristan~
These birds look great - and your thoughts on painting are right on the money. Long "strolls" through gumbo are no place for cork birds.
A couple of thoughts:
When you epoxy the heads, bill, etc, consider sprinkling some fine sawdust onto the wet epoxy. It gives a nice tough skin with no shine that takes paint beautifully.
I might go a little heavier with your stakes and sockets. How about gluing a length on 1/2" PVC pipe in as the socket, then using 7/16 dowels for legs? (3/16 bends a lot) The additional weight would be negligible.
Have you looked for dock foam? It saves the laminating and is a nice dense material.
I look forward to seeing the rig.
All the best,
SJS