How to deter Red Kites

In the summer I like to dine outside with friends. I have a table with a fire pit in the middle and a large umbrella. The Red Kites swoop down underneath the umbrella and right above the lit fire pit in order to pick up food (cooked meat) from the table.  I thought the umbrella and the fire would be enough to detract this scavenging, but it is not. They come very close to humans and my dog they are not at all scared, we on the other hand are very scared.  What else can i do to prevent then swooping down and taking food?