Excuse me a moment whilst I go and quieten my closest friends! "Keep quiet you lot! I'm trying to be serious here for my food blog followers".
Sorry about that! Right where was I? Oh yes, the answer to the question is; you should always stuff your bird if cooking it whole as this will aid in keeping the breast meat moist.
If you cook a whole bird with its cavity empty, then the heat will circulate in the chamber and it will rise and dry out the breast meat.
You can if you so wish just place some vegetables inside the cavity, vegetables with moisture are best like potatoes, carrots, leeks, onion or better still citrus fruits like lemons. These will not only help keep the breast meat moist but they will offer aromatics to the flavour of your meat.
Don't forget to remove the wishbone before stuffing your bird from both ends, I use an oyster shucker to do this as it avoids any cuts to your hands.
If using breadcrumb based stuffings, whether homemade or shop bought, then cook them first before placing inside the cavity. The reason for this is simple, an oven roasted bird will cook from the outside inwards and if it has to reach and cook the stuffing aswell then the meat is at risk of drying out. However if the stuffing is already cooked then the bird only needs to be cooked through and the cooked stuffing will look after itself.
For the best results, brine your bird overnight before using as this will enhance the flavours, use 30g of salt to each litre of water used and add any herbs and spices to your liking, avoid using any metallic containers. Make sure you thoroughly dry your bird off before cooking.