These are splattered bird droppings on the tarmac. Made by the birds on a horizontal canvas using the force of the whole body assisted by gravity, in true Jackson Pollock style. Or did Pollock learn the technique from them....
Thanks for the suggestion Anders Wahlund, but I don't know about getting rich by selling this art . I might be sued by PETA for copyright infringement of the art by the birds . Remember the monkey business that photographer David Slater was caught in