Perhaps a Loner

Our window box (a small plastic job) has largely been the preserve of a single bird this Fall.  That would be a male House Finch (example shown) with bad eyesight.  I'm sure of the last because I can often sneak up on him without the bird seeming to be aware of me.  And the bird's intrinsic behavior at the feeder leads me to suspect something else.  House Finches are very gregarious birds.  That this one consistently works alone makes me wonder if he's an outcast... maybe conspicuously sick, injured, aged... who knows.  The feeder gives him a safe place to eat and be left alone.  Plausible?  I continue to observe in hope of more insights.