No you can't enter a duck and do a no-show. It looks like the show has cottoned onto that. You only get your tickets once you have delivered your bird to the poultry tent, normally on Friday evening or Saturday morning.
http://www.royalhighlandshow.org/assets/downloads/POULTRY_Schedule_2011.pdf"Entry to the showground with birds will be by letter of authority.
Re-admission wristbands, to enable exhibitors access to the show, will be issued by the stewards
when the birds are delivered into their pens - only one wristband will be issued for each exhibitor
number and only if that exhibitor makes five or more entries. Wristband access is only permitted
via the main show entrance gates."
The entries are still open for poultry. Remember, if you enter the poultry, you will only get tickets to admit you on the Saturday/Sunday as those are the days the poultry are exhibited.
Beth