Sometimes Nothing Makes Sense

When I observe a new behavior, I try to explain it.  Sounds easy.  But there are times when nothing makes sense.  Here's a new one by this American Robin.  The bird was seen roosting just below the feeders.  I have never seen this behavior before.  Is the robin sick? not likely...it regularly got up and flew around.  Camping out to discourage other feeders? no..many other birds were on feeders and ignored by the robin.  Cold? Ha! ha! not at room temperature! (70F outside)  So I'm stumped.  All I can do to sate my curiosity is to watch future behavior and see if I can better understand.