Yes, you do because you need to let the foliage ripen, so you can't mulch over them.

It probably depends on which grade of bark mulch you plan to use and how thickly you intend to apply it.

If you're thinking of bark pieces around the size of the top joint of your thumb laid about 2-3" thick then the daffodils will have no trouble coming through next year, in my experience. And fertiliser sprinkled over the surface of the mulch does wash through - depending on your rain supply or watering regime.

If the daffs are still in full leaf then mulch around them as if they were perennials and cover over once the foliage has died back.

They seem to get through a cambium mix OK but the larger grades of mulch can be somewhat oppressive for young leaves pushing through.

Vetivert8, I had the same question, thanks for the detailed answer. :)