The safest and most natural way of providing food for birds is by landscaping with native plants. Audubon’s Native Plant Database provides an easy way to look up plants native to your specific area.
This method is obviously more labor intensive than simply hanging a few feeders, especially when first getting started. Additionally, HOA regulations can sometimes be challenging to navigate. However, as someone who loves gardening as much as I love watching birds, I find it immensely rewarding. You don’t have to replace your entire yard or go war with your HOA to landscape with native plants. Just keep native plants in mind next time you need to fill a gap in your yard.
I just recently replaced an invasive Mimosa Tree sapling with a native alternative that attracks hummingbirds, Red Buckeye. Native plants have the added benefit of drawing birds that don’t visit feeders into you yard. Things like native oaks, willows, cherries, and birches will attract warblers and other insectivores. Native plants also support more than just birds. My Red Buckeye provides nuts for the squirrels and is a host plant to Saddled Prominent Moths.
I highly recommend this article from the Lewis Ginter Botanical Garden and any books by Doug Tallamy.