"David Hill" wrote in message ...
"...........In the US we produce easily 2 tons of wheat per
acre, which will cover the caloric needs of 7........."

You might do this on 100 acre fields where the birds are spoiled for choice,
but you try a small plot of grain and see just how much the birds have.

You may or may not be right. My birds even ignore the winter feeder I
put out for them, and 10 lbs of bird food go unfinished (and I live in
a place with plentiful wildlife) over the winter. As far as I can
tell, at my place the birds will eat seed only under extreme need -
they need the bugs more, and can find them even when the ground is
frozen (winter berries are also reltively plentiful). The squirrels
don't ignore the seeds, though, so I agree that one would have to
continuously kill & eat squirrels to save the crop. So, 1/4 acre
instead of 1/6?