That's actually a really good idea! I think i'm going to do something like that. Since I'm starting out, now is the perfect time!I keep track of what comes in, and what it costs, and what goes out and its price, minus a few cash transactions for eating eggs I forget about.
I just keep little doller store notebooks for each species (ex. khaki, peking, turkey). If the amount changes me on taxes (which its unfortunately never been high enough to do) Id report it.
At the least, its a good record of where all my funny money goes. The view in the backyard!