Preheat the oven to 230°C/gas mark 8. Season the birds inside and out with salt and black pepper and place the sage leaves in the cavities. Rub the breasts with the butter.
Place in one or two large roasting trays and roast for about 15 minutes, keeping them pink and basting with the butter from time to time. If you are cooking widgeon, allow an extra 10 minutes or so, as they tend to be twice the size.
Serve the game birds on wooden boards or a platter, with gravy or a rowan jelly. Buttered sprout tops tossed with chanterelles or lightly roasted chestnuts work a treat and bread sauce is a must.
If your game birds come with livers, these can be fried quickly and spread onto toast. Serve with a gravy or a jelly, such as hedgerow, cranberry, rowan, quince or rosehip.