These devices provide passive plumbing for avian waste, including a collection surface and transport system that gathers waster into a container for nutrient recycling and fertilization.
The provision of plumbing, a precondition for urban life, allows for healthy high density co-habitation. In turn the high density of persons and resources fosters the efficient exchange of salient information--in people, pigeons, sparrows, mice, ants and other social creatures. In the 19th century, the popularized water closet (named in contrast to the earth closet) demanded a ready supply of running water, which led to overflowing cesspits, and civic infrastructure for transporting the sludge into waterways, eventually, via water treatment plants. Organic materials otherwise incorporated into the terrestrial nutrient cycle, are now released into waterways. While the human toilet depends crucially on the innovation of the S curve in toilets, and ingenious way to trap smells, this does not address the contemporary crisis: nutrient depletion of the terrestrial ecosystem and the nutrient enrichment--excess--of the aquatic and marine systems, as millions of tons of human excrement and industrial waste are rerouted via and into waterways.
The public toilet for the pigeons, exploits only the ambient condensation and precipitation to "flush" the device, but combines the surface of collection with surface for transportation. Nitrogen, phosphorous(P) and other organic materials are then available to distribute in nutrient depleted soils, rather than washed into rivers. Moreover the open design of this system avoids the other activity that public toilets have tended to attract.
Without plumbing technology and water treatment plants, other technologies would not be possible, so extending this convenience to the pigeons can turn our attention to the communication technology that translates for the birds