I imagine you'd be VERY surprised how many aircraft have been grounded due to bird strikes. Keep in mind that it doesn't have to disable the aircraft in order for it to be grounded. It costs us a LOT of money to have an aircraft on the ground waiting for inspection and if it requires repairs this price grows astronomically by the hour.
You'd think that a War Worthy aircraft would not be so "Fragile" but you're be wrong. Take this Canadian Hawk-115 from BAe that CRASHED due to a bird ingestion in/around 2004. This video is from two entirely different flights (2 different airplanes) combined to add more DRAMA to the finished product. Keep that in mind when watching it but remember a BIRD did take this aircraft down... down to Terra Firma
Now image what the same bird would do to the windscreen of a non-impact rated aircraft. Most GA aircraft do not have impact rated windscreen and a bird impact at the right place will destroy the windscsreen and introduce it AND the bird remains in the face of the cockpit personnel.
Here is a good example:
First of all your "Drone" is a lot more rigid (
especially the battery and motors) than the brittle components of a bird. That makes a WORLD of difference in damage amount. Don't believe me? Have someone toss a wet beach towel at you from 3' away. Now freeze the same beach towel (make sure it has the same amount of water etc at before) and have the same person throw it at you from 3' away. Notice any difference in those two situations?
You don't understand RADAR and how they work. A large sUAS may show up on some units but the returns from a radar are intentionally FILTERED to disregard items the size of birds. Otherwise the radar screen would be so full of clutter you wouldn't be able to get any data from it. Before you get to carried way discussing radar you also need to know that unless the aircraft (or lets say BIRD) is carrying a transponder it won't show a viable return on ATC radar. That's a whole different technology than object avoidance radar.