Just to confirm the obvious. Downvotes are expected but OP you should read this.
They are close enough to see that they are quad copters, and they make a buzzing noise, correct?
There have been a lot of UAP flaps where the objects (not quad copter looking) will fly low over the countryside, just above the tree-lines to much higher. They usually make no noise aside from reports of static or screeching or electronic interference.
Unlikely to be the case but if so, report to your countries MUFON type department and get as much evidence (video with sound, drawings, time and date, etc) as you can.
There is something else out there, whether it's military black projects mapping areas or what have you, and it needs to be documented.
If it is for sure quad copter drones, you can get a device to blast the 2.4Ghz spectrum for a short time and make them 'phone home' and the operators will stop flying them over your property once they realize something wrong keeps happening when they do. Legality varies.