On Thursday, I watched two juvenile hummingbirds approach the feeder.  
For several minutes they did a kind of dance, each equidistant from the 
feeder, moving back and forth, side to side, neither getting closer 
than the other.  This went on for several minutes until they both flew 
off, nether having fed.  This kind of movement I have seen in otters 
and in squid, but never before in any bird.