You had me excited to read about this all day, but I was traveling and couldn't get to it until now.

I read the study paper and for the most part there wasn't too much more to it than what you said, but then the conclusion has me a little confused.

The fact that parents responded to a manipulation of UV reflectance of their offspring can not be due to UV coloration, because owls probably do not have a VS or UVS cone (Bowmaker & Martin 1978) and, at night, there probably is not enough light for colour vision. It is possible that the measured effect was due to a change in perceived brightness mediated by scotopic (rod) vision. Compared to diurnal species, owls have very few cones in their rod- dominated retina (Hart 2001). Owls, like some bats (e.g. Winter et al. 2003), may have a UV- transmitting lens and cornea and so the secondary (beta) peak of the pigment in their rods would capture UV light contributing to achromatic vision at low light levels. It is also possible that, even at low light levels, photopic discrimination was involved, but again the effect of UV would be via the stimulation of the beta peak of pigments in the cones. It has been reported that owls have cones containing oil droplets that are either colourless or only a pale yellow (Walls 1942), which presumably transmit UV light.

So if it's not a coloration difference, does that mean they are just seeing a brighter type of grey (greater amplitude) or are they seeing something else?

I'd like to learn more about their UV seeing abilities, but I feel in over my head. I feel this paper is pretty jargon heavy.

Very interesting stuff though!