I have used electronic devices to repel rats, moth balls, carpet fresh, chili pepper. These items around the perimeter may help. Also rats can't stand the smell of lavender or mint. If you remove the food at night it will eliminate the problem.
Your birds are gorgeous.
Also, Rat Terries are trained to kill Rats instantly, I had four at one time, I can verify this, better than cats. Good luck.
Mix chilies into the feed, the pheasants won't mind it, but the rats won't be happy about it.
@Millwright There are bird seed mixes that do this to keep out squirrels.