You could cut them down now or leave them for the birds. They like the seed heads, then cut them in the spring. They are self seeders, so you may want to cut some and leave some. Either way, it's up to you.

I'm with anitamo. It's not as tidy, but I tend to leave mine standing for the birds, then cut back in the spring. Either way, cut them now or later, the plants will do fine.
Connie

Thank you Anita & Connie. I am new at gardening so was not sure. I would like to tidy up the place so I am thinking you mean that I can cut them down to ground level. Is this right.

I would leave the foliage up if these are first year perennial plants. In my cold zone it is pretty much standard practice to not hard prune new plants to the ground for their first winter. Of course, rudbeckia and coneflowers are very hardy (and you don't have your zone listed) so this cautionary practice might not be necessary at all.

If any of your coneflowers are the expensive new color hybrids, I would definitely not cut them to the ground. Anyway, August is really early to cut them back here, unless there is some sort of foliage problem. I'm still getting some new blooms on Sundown Echinacea and the self-seeded ones are still growing and need their leaves. My Black-Eyed Susans are in full bloom, and so are my annual rudbeckias, although these are starting to get messy looking and I may do some trimming.