even when we didn't have the birdfeeders, birds would hit the glass. this is not the first time it's happened, over the course of 19 years i can think of several other times.
we have had the birdfeeders for a long time (maybe a couple of years) and to my knowledge this is the first time a bird has hit the glass since.
so to me, having the birdfeeders versus not having the birdfeeders has no effect on the number of birds hitting the glass.
if we took them down or moved them further away, the odds are still pretty great that at some point, a bird will crash into the glass again.
thusly, i believe that if something in the area is at fault for the birds' deaths, then it is the door, not the feeders.
and what are we supposed to do about that?