The oval dropping is enclosed in a membranous sac which makes it easier for the adult to dispose of it well away from the nest and avoid revealing its location to predators.
幼鳥的排洩物呈圓形，有一層膜包著，以便於成鳥將之銜至離巢較遠處丟棄，避免暴露鳥巢位置，招引天敵。