what is it?

The birds are very messy and tend to throw seeds everywhere when picking through the large feeder.  I assume they do this because they are looking for their favorite bits.  Having been lazy not weeded very well I found a few large plants growing under the feeder.  At first I thought it was corn which was pretty cool.  So we left them.

Obviously from these pictures, this is most definitely not corn.  I'm not really sure what it is.  It doesn't look like my pictures of either amaranth or millet so I'm stumped.

Unfortunately I don't have the label from the birdseed so I can't even pick it out from there.  Wondering if I should harvest it for the birds for winter or if it's edible by humans.  Anyone able to identify it?