It's inevitable that some larger birds may find a birdfeeder and come to dine. Discourage crows, starlings, and other such birds by flapping cloth at them. A strategically placed scarecrow may keep crows at bay. Hawks will sometimes hunt birds while feeding but the number of birds they kill is quite low. Many bird affectinados enjoy watching the hawks but to discourage them, remove the feeder temporarily and they might seek other sources. Never trap, shoot, or poison hawks because to do so violates state and federal laws.
If birds often crash into a particular window or if some birds - northern cardinals and mockingbirds in particular - attack a window, put a stop to it by pasting something opaque on the window. A poster, newspaper, streamers, wind chimes, or balloons will do the trick and turn birds away.
One of the newest dangers to our feathered friends is West Nile Disease. The disease is transmitted by mosquitos to birds and is now found in most of the 48 continental United States. Birds may develop immunity over time but at present there is little bird watchers may do. If more than one dead bird is found without cause, contact local authorities so that it can be tested for West Nile Disease.
Other options for viewing birds can be found in zoos, some museums, and aviaries. Some states have conservation areas where birds can be viewed in the wild. Check local listings for venues to watch birds and enjoy the show.
Keeping cats indoors can help birds. Even domestic cats will hunt birds. Even having cats declawed and wear a collar doesn't always prevent cats from hunting birds.