My intent isn't to engage in argument with you, but I'm curious, by that line of reasoning do you feel the same about K9 dogs used to take down criminals who may be armed?
Not the OP, but K9 is the alternative to using a human for the same purpose. Birds in this case were suggested as an alternative to using a $1 shotgun shell.
The birds are theoretically a lot more capable. Birdshot from a shotgun won't work well if the drone is trying to avoid it by flying a bit too high, too far away, too fast, etc. A bird of prey stands to be a lot more successful if the drone pilot isn't trying to make things easy.
The risk to the bird shouldn't be ignored. It seems to me the use of birds in this way is most defensible when human lives are plausibly on the line, such as when drones are negatively impacting firefighting efforts.
Not to mention that you can't use birdshot in certain areas because the bbs are going to come back down and you don't want to hurt a dozen people because you have to take down a drone in the middle of NYC.
Birdshot is nice when you're in the middle of nowhere and no people are downrange, but you shouldn't fire a fucking gun when people are down range.
Edit: I should mention falling birdshot is fairly harmless. But I'm thinking lower angles, high rise buildings, or when you're taking down a drone near an airport (which is one of the major concerns). There are people and sensitive objects down range. And even with birdshot you should never shoot when there are people down range. Just be responsible with your guns.
The first time I tried to fly a drone I broke all four of its rotors and _scratched the glass_ on my patio door. A bird would almost certainly be severely hurt by the rotors. You can't seriously make the argument in favor of using birds. In fact, if there is an argument to be made here it's in favor of the drone immediately powering down the rotors if it notices a bird approaching.
It seems plausible to me that a bird of prey could learn how to attack drones from safe angles; I don't think a bird would necessarily be hurt by the drone, but I concede that it's a highly possible outcome.
Restricting the use of anti-drone birds to scenarios where human lives are on the line seems like a reasonable compromise, and I do seriously make this argument. I'd further consider it reasonable to hold the drone pilot legally accountable for any harm to the bird.