As an example, select March 3 and watch the explosions of blue that moves from northern Texas to eastern Arkansas.
A classic example is Oct 14. As dusk approaches, birds take flight along the east coast. The explosions of blue are birds in other locations doing the same thing at dusk arrives in each successive location from east to west. It's pretty spectacular. Of course, weather patterns also show up, which also helps in telling birds from storm patterns. Lastly, the static green dots are ground clutter, notably wind turbines in locations such as northern Texas, south western Kansas, and central Illinois, among others.
When combined with the website below that shows wind direction in graphical form, they can be very useful tools to help predict "very birdy" days.