We generally feed the birds with various nut/fat balls and a 'feeding house' through the harder winter weeks - this winter was so mild that we have not needed to do this at all. (A poor year for the suppliers of these products.)

When we lived in a flat, we were warned off feeding the birds on our balcony by our landlord. It was claimed that they dirtied the wall and windows below. So we kept the house clean and the birds staved...