One of the sure signs of spring is the sight and sound of Red-winged Blackbirds as they perch on the tops of cattails.  These Blackbirds are most frequently found in marshes, swamps and other wetlands.  They are among the most abundant native bird species on Cape Cod.  They typically make their nest over shallow water in a dense stand of cattails.  Red-winged Blackbirds are black all over with black eyes and a pointed bill.  The most distinctive field mark is the bright red and yellow shoulder patch on the upper wing.