“From a mechanical point of view, drones behave differently to birds and also weigh considerably more. It is therefore uncertain, whether an aircraft that has been successfully tested against bird strike, would also survive a collision with a drone.”
Source: Dr. Sebastian Schopferer, one of the scientists working on a programt at the Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut, EMI -- which is now planning to build a test bench for recreating various collision scenarios with complete drones.