[krapht]

I can't speculate on what's actually on US Navy warships right now, but I'm telling you commercially you can distinguish birds from drones under a kilometer away today. The knowledge has been around on how to do so with radar since 2006 https://ieeexplore.ieee.org/document/1603402, but even without that, there are numerous combined radar-camera surveillance systems out there for accurate target classification. Not like you don't have time to cue a camera to look at an interesting radar target when it's travelling slowly like a UAV might.

[runjake]

The military’s been able to distinguish this since the early 90s — at least. And yes modern drones didn’t exist in the 90s but other similarly-sized machines did, eg balloon-mounted telemetry devices.

Citation: personal experience with those sensor systems.