There were at least 20 to 30 dragonflies just hanging off a wire that runs over a small pond in my garden.
No interactions present.
What a fascinating collection.
Incidentally, that mark near the end of each wing is called a Pterostigma - I've seen one article that suggests it is to give the wing stability in flight. All dragonflies have them, though they vary in colour according to species.
Lat/Lng: 52.7, -3.1
OS grid ref: SJ2722