I have observed bumblebees hover over an a abrborvitae (Thuja occidentalis) hedge. A bumblebee will hover in a in one spot over the hedge for about 5-7 seconds, zip to another spot, hover for about 5-7 seconds, then another spot, then another. The bees will never land on the hedge. At any one time during anyone day, there will be only one bee hovering over the hedge. This behavior will go on like this all day.
Why do the bees do this?