Seems logical to me...

but I guess it mustn't be that obvious to everyone given that this warning is sized for a highway overhead, but is on the fence by a pedestrian walkway.

This is the riparian area of the Rio Salado, just East of Tempe Town Lake. There's a lot more water in the spring as the snow melts in the mountains to the north-east. At that time of year this area is loaded with Egrets, Herons, and smaller wading birds. If I leave work at dusk, I can see them from the highway, settling into the trees for the night.