High levels of liver bile salts in their digestive systems allow them to digest waxy fruits like bayberry, wax myrtle, juniper, and poison ivy, letting it winter far north of other warblers.
Until 1973, they were considered two distinct species—the eastern “Myrtle” Warbler (white throat) and the western “Audubon’s” Warbler (yellow throat)—before genetic studies combined them into one.