How did the experimenter measure miss distance in pitch darkness? IR illumination is presumably out in case the owl was able to see it, and I didn't think thermal imaging was a thing yet in the late '50s.
> To eliminate the possibility that the owl was [...] detecting heat from the body of the mouse (for instance, by sensing infrared light emitted by a warm body), the experiment is repeated with a mouse-sized wad of paper dragged through the leaves
(source: I used to volunteer at a Raptor conservancy).
It gives a good visual as to how much air is being moved/disturbed during the flight/glide of each.
It brings to mind the question of why nothing seems to have evolved two pairs of ears with separate openings; We're all working with varying degrees of spectrum shaping to achieve up-down sound localization. If you wanted to design a robot that can perform sound localization, the obvious answer for that extra dimension would be to just double up on the microphones.
What do ears do? Transduce pressure vibrations into intelligible signals. If this is our understanding of an 'ear', we never really need more than two but instead need either binaural or non-binaural/decoupled. Beyond that, what does having more openings grant us that we're not getting with all the other pressure-sensitive organs we have? (namely all of our skin, some specialized tissues in other animals)
But binaural gives us a dramatically easier grasp of left-right localization. For a lot of things, that's all you need!
But the animal kingdom is large and diverse, and high-fidelity up-down-left-right localization would be similarly valuable in numerous places. It is a little bizarre to me that there's no freaky bat or something out there that evolved an extra molar into its own little secondary sonar sensor, with a centimeter of baseline from the normal set. Because with robotic sensors it wouldn't even be a question what to do.
Current drones are not very loud (well, Shaheds are), but if someone could make them more silent, they would be even harder to detect. Maybe covering them with a structure similar to owl featchers would do it.
I am not an ornithologist, but I’m assuming that’s a typo for barred owl?
