So, why to some birds and some critters wear masks?

-Good question! I searched high & low ("Googled"), to see if there was any literature on facial- mask coloration; much of what comes up is related to mask protection for avian flu! :o)) --however, this link, which represents a summary of the complete document, shows promise: ( http://adsabs.harvard.edu/abs/1979RSPTB.287...63B ) -the hypothesis is that it is related to initiating negative response mechanisms in the predator! (kinda like when the Eastern Tiger Swallowtail caterpillar suddenly brings it's head up, with those two prominent "eye" spots, to make a predator think twice about eating it!)

Beautiful shot!