Male Satin bowerbirds (like the bird pictured here) (Ptilonorhynchus violaceus) build specialised stick structures, called bowers, and they decorate the area around them with blue and yellow objects. Those objects may be natural objects such as the yellow leaves, petals and snail (bottom right) you see in this photo, but when close to human habitation they are often artificial items, mostly plastic. Females visit these bowers and based on their inspections choose which male to mate with. I believe the bowerbird pictured here is practising a display – holding up a yellow petal in a striking pose – that he will employ when a female comes.