A crisis of sparrowhawk proportions

We are having a bit of a crisis. 

All of our garden birds have started fledging and there is about 20 on the feeders at one time. However, our dear local sparrowhawks keep popping down, robbing one and going again. I understand they have to feed too, and it is natural, but are there any deterrents? I particularly don't want Great Spotted Woodpeckers or sparrowhawks taking the only nuthatch fledgling we have had in a few years. (little jamie :( ) 

My mother and I love the woodpeckers coming down, and they also have a fledgling, and the nuthatches keep having a bit of a stand-off with the woodpeckers, and I don't want them to keep fighting everything!!!! Any ideas??