I don't have a bird feeder and yet a huge variety of birds feed on my garden.
It's just a matter of selectively sparing some plants over others.
For example many small birds will eat kale and brasica seeds which are tiny and black like a poppy and each plant produces a huge abundance.
Another favorite I noticed among the small birds is wild Lambs Quarter seeds, same thing, thousands of small seed per plant.
And if you really can't help yourself, you could learn about animal husbandry and raise chickens for eggs, they love to have about 20% of their diet as scratch grains. I like to ferment and sprout the dried grains to make it easier for my hens digestion. Did you know chickens are omnivores and eat nearly all the same foods as humans? No wonder we keep them around, they literally eat all the left overs!
For more details check out this video: