In reply to briansy:
Over the years I've noticed, in my garden at least, the majority of the birds love sunflower hearts put inside Feeders and the Greenfinches love Sunflower seeds with their husks in the Feeders.
The ground feeding birds like the mixed seed but if sunflower hearts are on offer, that goes first. This may be problematical from a first floor balcony 😀
Today I saw my first Wren in my garden and I was over the moon.