About six weeks ago I lifted one of my hives and it seemed very light, so I started feeding with fondant and about 3 weeks ago I put a sugar "cake" on top of the frames. When I put the sugar cake on, I also added an Imirie shim to provide more space between the top of the frames and the bottom of the inner cover. Having the Imirie shim in place also provided an upper entrance in addition to the bottom entrance which has an entrance reducer on the smallest setting in place.
It's a warm but windy day today and the bees in this particular hive are pretty active, especially at the top entrance around the shim.
Am I observing normal activity or am I observing robbing? How do I tell the difference? And if robbing, should I close off the top entrance?