As soon as the birds are paired, you can place nesting material in the loft. Some fanciers place the material inside the nests. Some place it on the floor and let the birds build their own nests. This practice also helps them exercise and wear off Winter fat.
What nesting material do you use? You can use straw, twigs, tobacco stems, or pine needles. Straw gets mushy as the squeakers ( baby pigeons ) get their droppings on it. It is also a good home for mites and lice. These pests live in the hollow stems of the straw. Straw is cheap and easy to get. Tobacco stems and pine needles are both great for nests. They both help repel mites and lice. Pine needles are cheaper. All you have to do is find a pine tree and rake them up.
While the birds are building their nest and courting, the cock will eventually get on top of the hen and mate with her. He will also feed her a milky fluid that helps stimulate her to produce the eggs.