What behavioral trait can often help focus identification on many Parulidae in North America?

The presence of a strong, clear song

While deep scientific classification separates warblers into different families across continents, field identification often relies on practical shortcuts. For many species belonging to the Parulidae family in North America, a quick indicator that aids identification—even before a clear view of subtle field marks like eye-rings or wing bars is achieved—is the observation of a strong and clear song. This vocalization is frequently a hallmark of many New World warblers. Conversely, observing foraging behavior, such as meticulously picking insects off the underside of leaves high in the canopy, is another recognized classic warbler behavior that remains useful across different classified groups.