You have a couple of options. You can provide shelter for the little birds to give them hiding places, or you can pull your feeders for a couple of weeks until the hawk moves on.
If you can get some old Christmas trees (make sure any tinsel is removed) and put them a few meters from your feeders, the birds can use them as shelter if the hawk appears. Keep in mind that the branches should be pretty dense--you want something with large enough spaces for your little birds but not so large that the hawk can go in after them.
Probably your best strategy, though, is to remove your feeders temporarily. The hawk needs to eat pretty frequently so if he's unlucky in your yard for a couple of weeks, he's likely to move on to better feeding grounds. Your little birds will stick around and when you start putting the feeders out again, they'll find them pretty quickly.
And congratulations on your successful feeder set-up!!! You don't attract hawks if you're not getting a pretty good crowd of song birds at your feeders.