I started writing a complex demonstration, but the intercept theorem, (Thales' theorem) indeeds shows quite nicely that from a ground station, tracking a plane

I started writing a complex demonstration, but the intercept theorem, (Thales' theorem) indeeds shows quite nicely that from a ground station, tracking a plane flying at (𝒽1,𝓋1) means the beam goes at 𝓋2=𝓋1*𝒽2/𝒽1. So, 5 m/s for a bird at 200m. That said, I was mostly imagining space-based stations. In the above case, I talked about ground-based stations at airports. Unfortunately, those would require high angular velocities, but would already be in bird-restricted areas (airports use all sorts of tricks, including drones, sounds, people chasing them, etc, to scare away birds). You could also conceivably drastically lower the beam energy output by using multiple beams that concentrate at a single point. Now, a fun calculation: what would be the tipping point between birds saved by not emitting carbon dioxide and birds killed by the towers, if there is one? One last point: I'd hazard that the bird is likely to change direction if it starts running into a beam and it has time to (ie, it is not killed "instantly"). This drastically lowers the dangerous altitude range, as the bird is less likely to fly in the same path as the beam (how likely was it in the first place? One would need to go faster than the other to catch up, but not too much to actually dispense the lethal dose? I haven't done the math, but I'd say it's quite unlikely).