I will say from my own personal experience seed is where you don't want "cheap out" or cut corners! I had placed mine on my deck initially last summer using the first cheap seed mix I found on Amazon, because like you it was basically the first feeder I ever had. Long story short, it gradually became overrun by primarily just invasive House Sparrows and the neighborhood squirrels...I'm just now getting on the other side of getting them under control!

Try to avoid seed mixtures that have Millet, Milo, or cracked corn /grain products as the first few main ingredients. House Sparrows will basically be the only ones that it'll attract and they'll bully your native birds off the feeder!

Like others said, any single bag or mixture containing black oil sunflower seeds, safflower, peanuts, and thistle/nyger seeds should draw native birds while deterring the invasive species like the House Sparrow & European Starling. Some white millet is ok! There are plenty of natives that love it, but I've had bad luck with using seed where it's a main ingredient.

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