The northern waterthrush looks to
many beginners like an undersized thrush, but it
is in fact a warbler. This species can be difficult to
differentiate from the Louisiana
waterthrush, which tends to have a
whiter eye stripe and less yellow or buffy color around the face,
throat, and underside. While the northern waterthrush is
sometimes spotted at Magee Marsh around the second week of May, the
Louisiana is much rarer at this site.
(public domain
painting by Louis Agassiz Fuertes)
The Wikipedia page
for this species provides more information, and is embedded below: