Common sunflower (Helianthus annuus). The wild form produces multiple heads that are a little smaller than the one big one found on plants cultivated for the seeds. I believe that the ones sold for wild birds can be used.

I certainly get excellent germination from the ones that drop from my bird feeders. Actually, I would think that any sunflower will produce seeds for the birds, as long as it isn't one of the fancy hybrids designed to not produce viable seeds. I'd try a variety and see which you (and the birds) like.

Martha