It has been know for several years that some birds see well in the UV range and that UV markings on windows, while not visible to humans, can be detected by birds and offer protection from window collisions. The UV effect might not be ideal for evey situation, as reported from this excerpt from research posted on the PeerJ web site.

“Glass windows cause more bird fatalities than one might think (Banks, 1976). Being optimized for flight, birds are lightly built and collisions with large obstacles often result in serious injury or death. Because the glass reflects the landscape outside (Fig. 1) or offers a more or less unobstructed view of items behind the window as well as the landscape on another side of a building, it may trick birds into believing that the window is an available flight path. As a consequence, the world-wide avian death toll from window collisions reaches billions each year, according to recent estimates (Drewitt & Langston, 2008; Klem Jr, 2009a).

The means to prevent avian window collisions include nets, screens or grilles that are placed at a safe distance in front of windows or densely spaced, visible markings applied to the glass directly. Albeit effective (Rössler, Laube & Weihs, 2007) these solutions diminish the aesthetic value of having window glass in buildings, and will impair the view of the scene outside. Since it was discovered that diurnal birds can see ultraviolet radiation (Huth & Burkhardt, 1972; Wright, 1972) to which humans are blind, reflective or absorbing ultraviolet markings on window glass have been proposed and tested to make birds notice the surface while the marking remains invisible to human observers. However, this seemingly elegant solution to the problem has had varying success (see Haupt, 2011). On the one hand, ultraviolet absorbing stripes on a window with narrow (5–10 cm) spacing have proven almost as effective as covering virtually the whole window with human-visible markings (Klem Jr, 2009b). On the other hand, field tests of commercially available UV-patterned glass have, under see-through conditions, shown an increased likelihood of window collisions compared to ordinary window panes (Klem Jr & Saenger, 2013).”

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