Bird feeding can be done year round.
Today we know that wild birds won’t lose the ability or motivation to primarily find their food in nature.
And there is also no danger of them feeding their nestlings wrong foods (except during breeding seasons with scarce natural food like insects).
It is important to have an easy to clean and hygienic feeding sites and to use high quality bird food (i.e. free of Ambrosia). Make sure you that the birds’ feces and food leftovers fall to the ground instead of landing in the food. That’s why the trend is moving away from classic bird tables towards tube feeders. Human food leftovers and bread are no bird food (not for ducks, geese and swans either).
Besides feeding birds it can be useful to offer water for trinking and bathing.