In the wrong places, birds can create big problems. They nest in sheds, attics, inside walls, and any other place that is dry enough to raise young. Trees that produce fruit, seeds, and nuts are preferred food sources. Streets lined with ornamental pear trees can birds near parked cars can make a mess. Nests built inside your house can cause health problems. Once bird feces dries and becomes airborne people can contract histoplasmosis, a lung infection caused by a fungus.