Big concentration of dragonflies on edge of savanna -- a lek? At least some look like saddlebags, Tramea genus, but others do not appear to have saddlebags. Mixed group?
The skimmers or perchers and their relatives form the Libellulidae, the largest dragonfly family in the world. It is sometimes considered to contain the Corduliidae as the subfamily Corduliinae and the Macromiidae as the subfamily Macromiinae. Even if these are excluded (as Silsby does), there still remains a family of over 1000 species. With nearly worldwide distribution, these are almost certainly the most often seen of all dragonflies.