While basic assorted bird seeds will cover a variety of bird species, you can be more selective with, say, black oil sunflower seeds. They may cost more but there is far less waste, and fewer sparrows. Finches prefer Nyjer or thistle seed, which requires a special feeder for the tiny seed. Bird diets will vary with the season. Summer insect eaters will switch to berries in winter, for example. A great way to attract woodpeckers or bluebirds is with waxworm-embedded suet (a processed cake made with melted fat mixed with seed, berries, waxworms, etc.). Choose a feeder designed for the seed or other food your birds most like.