The two North American waterthrushes (Louisiana waterthrush and northern waterthrush) are confusingly similar, and both look more like tiny thrushes than warblers. For both, the constant tail bobbing as they walk is an excellent identification clue. Males and females are similar, and they do not change appearance seasonally. The Louisiana waterthrush is distinguished by its broad white eyebrow; its plain white throat; and bright pink legs.
The distinctive song of the Louisiana waterthrush starts out with two or three down-slurred notes and ends in a sputtered jumble: tee-yew, tee-yew, tee-yew, chicky-chick-a-chur-wow-chik! This bird also gives a loud and sharp call note—chink!
To determine which waterthrush you may be watching, examine the head. The Louisiana has a bold white eyebrow and plain unstreaked throat. The northern has a finely streaked throat and narrow, often buffy (not white) eyebrow.
The Louisiana waterthrush spends spring and summer along small flowing streams and ponds throughout the eastern United States. Breeding territories are formed in a narrow corridor along streams.
Lots of experienced birders struggle to tell the waterthrushes apart. Fortunately, the two species have completely different songs.