‽Bros

Because birds excrete pasty uric acid with their stools rather than urea in urine as we do, this component of their waste may be white in color when dry, and spread in a pool around the solid waste. In the case of these pigeons, the color of the solid waste was green, a factor influenced by the color of their pellet diet. You may see how the underside of the cage papers display a sort of watercolor created by the pooled uric acid carrying pigment with it from the accompanying stool.

Is there a secret message here? All theories accepted via manila envelope.