Artificial light assist crows in watching for owls. I have noticed that many urban crow roosts are not located in nice dense trees where the crows would have microclimate advantages, such as protection from wind or cold. Rather, the crows perch out on the tips of bare branches of leafless deciduous trees. I was quite surprised by this at first, but then I noticed that many (most?) roosts are located near sources of bright illumination, such as streetlights and parking lot lights, like the lights at the Auburn prison and Syracuse University. It makes sense for crows to like "nightlights" to protect them from their biggest bogeyman, the Great Horned Owl. Crows don't see well at night; owls do. Crows near street light could see approaching owls. Also, if a crow gets scared out of its roost in the middle of the night (presumably by an owl taking crows), in lighted urban areas the crows can see where the predator is, and perhaps more importantly, can see to find another perch. You can imagine that flying blindly into the dark is not something any bird would choose to do. I was surprised at the amount of activity at the Auburn roost well after dark. The crows were still making a lot of noise and even flying from tree to tree. In other roosts I have watched that were in darker locations the crows quieted down rather quickly and no movements between trees were seen shortly after complete darkness.