What should I do with my sunflowers when they have finished?

1- leave the stalks for the birds
2- cut the heads, remove the seeds and leave them for the birds

Alternatively, leave the heads on theplants and the birds will feed off them throughout the autumn and winter. Or you can just cut the heads off and lay them in some branches somewhere, even on the ground, and the birds will collect the seeds - remove the sunflower plant, or cut off at the base.