Window hazards to birds

We lose several of our birds every year from their crashing into our windows and breaking their necks or otherwise killing themselves. We now have a bird graveyard which saddens us every time we add a chaffinch or siskin, even the occasional swallow. Sometimes they simply stun themselves and recover but often they are not so lucky. One time, a bird hit our kitchen window so hard it left a clear imprint on the glass of its shape - clear enough to take a photo of, wings, wingtips, body, head and beak, all clearly outlined. Is there anything we can do to help prevent the birds flying into the window? We've tried windchimes and stickers.