Readers with long memories may recall my mentioning that I'd setup an experiment during the last week of my 2012 screech owl nesting. The experiment was a home-brew motion sensitive trigger for my digital SLR camera, with trigger and SLR mounted such that they could catch the adults as they flew back and forth from the nest box. (You can see the sensor in the photos; it's the white plastic thing with the exposed pale wood behind it, mounted under the owlet rail. The clamp on the bottom edge of the nest box is providing mechanical isolation for the cable running to/from the motion sensor. Yeah, it was a kludge, but you have to get real-world experience before you can know how to finalize a design.) The experiment worked, albeit with a host of first-time-in-the-field problems that meant the experiment lasted only part of one night. Nonetheless, it was worth nearly being killed by a folding ladder with a very poor sense of timing about when it should fold, the frustration of having to cancel the experiment after a matter of hours, etc., because it produced the photo below.
This photo shows the delivery of a june bug, probably Rhizotrogus majalis. And I believe it answers my question about the more-or-less round, white food items that I've seen, via the internal infrared camera, delivered year after year, but which I’ve never been able to identify. The beetles roll-up, to the extent that they can, into a defensive shape, and their shells reflect near-infrared light well, so they appear white in such illumination. Combine that with the low-resolution of standard-definition closed circuit video cameras, and there’s not much to go on in terms of making a species identification. However, combine this high-res, color external shot with the internal shots that followed, and the mystery is solved, at long last.
The motion-trigger experiment produced some other photos of interest, too. I’d intended to post all of them sequentially with commentary, but since I keep failing to do that, I’ve started with my favorite, and will take it from there.