Birders affectionately refer to this species as "butter-butt," since its bright yellow rump is an eye-catching and diagnostic field mark throughout the year. Bold black stripes on the side of the crown, with yellow stripe confined to the top of the head. Or take action immediately with one of our current campaigns below: The Audubon Bird Guide is a free and complete field guide to more than 800 species of North American birds, right in your pocket. Upload your best active weather photos and videos or watch them in our new searchable gallery. Lives of North American Birds.