There is not a lot one can do. Hawks have a hunting territory and frequent these areas throughout the day. When they see a lot of birds concentrated in one area, they either wait and hide and launch a surprise attack or they chase them through the trees. They are sneaky and persistent. They will keep returning to your feeder because they know that birds are there frequently. Most birds will see the hawk coming and will leave before the hawk reaches your feeder area or they will dive for cover if the hawk catches them by surprise. This is why you should place your feeders near shrubbery, especially evergreen trees. I don't think it is a good idea to place feeders under trees as the birds need to see all around them and watch for the hawk or other predators. Having cover nearby is ideal. I have seen a cooper's hawk catch starlings and mourning doves in my yard. It is terribly sad. One dove was just sitting on a branch and the hawk came out of nowhere (it was hiding in cover nearby) and grabbed the dove. The dove did not have a chance as it happened too quickly. I have seen dove feathers near the feeder as well. I try to clap my hands or make loud noises to scare the hawk away. I also blow whistles and a children's play flute. It spooks the hawk a little but it never leaves the area entirely. The owl on the other hand does not like hand clapping or loud sounds and usually leaves much quicker. The hawk is seen around the feeder much more often in the winter and is much more aggressive on colder and snowier days when its other food sources are scarce. You will know a hawk is around when the birds are nowhere to be seen or are completely still and do not move. You will want to be very careful if you are trying to scare away the hawk not to scare the birds. They might be flushed out of hiding and into the hawk's talons. You can take the feeders down for awhile and hopefully the hawk will hunt elsewhere and put them back again after a couple of weeks. Birds live difficult lives, especially in the winter, and as much as I hate to say it, hawks have to eat, too and it is not easy for them to catch prey. I have seen the cooper's hawk in my backyard try and catch a starling and crash right into a tree trunk and it flew away but we will never know if it was injured. I have also witnessed owls crash into the side of my house and into the sliding glass door in pursuit of either a squirrel or bird. They were unsuccessful in catching their prey. I protect my backyard animals to the best of my ability and have saved many lives but in many cases, you cannot win against nature especially when these raptors are hungry.