Hey Ben, there's an easy way to pose pigeons and Antlions.
First off, spawn a bird/antlion NPC. Set the phys timescale in the admins options menu to 0, and kill it (there is a weapon in toybox that kills it without leaving any bullet marks). Then, Freeze all the major joints (try to freeze it all if you can), and set the timescale to 1 again. If it didn't tumble over dead, it means you correctly froze all the major joints. Now save it to adv dupe, and you can use them whenever you want!
Gmod 10 doesn't have phys_timescale. I think.
If so that would be helpful.
Anyhow, thanks everyone for the comments.