The acidity in bird guano (a.k.a. droppings) defaces stone and metal, attacking the substrate of a building to cause permanent damage.

	Pigeon, n. To others, a dove, homer, squab, pouter, turbit, tumbler, roller, or fantail. To BirdMaster™, a sitting duck.
	Starling, n. A usually dark, oscine bird known for gregarious behavior, except when it encounters BirdMaster™.
	Sparrow, n. A small chiefly brownish or grayish Old World oscine songbird. Best enjoyed in the wild, where BirdMaster™ sends it.
	Finch, n. a songbird with a short stout, usually conical, bill adapted for crushing seeds. BirdMaster™ dashes its chances to live in human structures.

Bird guano can damage structures.