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Tucson Audubon Society
Dastardly Duos
Northern and Lousiana Waterthrushes
by Larry Liese
Illustrations by George C. West
(Reprinted from the September 2003 Vermilion Flycatcher newsletter.
To receive the newsletter in the mail, become a member of the Friends
of Tucson Audubon.)
Remember
that song about the red-red-Robin going bob-bob-bobbin’ along? That’s
what I think of when I see either of this month’s duos. Both the Northern
Waterthrush (Seiurus noveboracensis) and its congener, the Louisiana
Waterthrush (Seiurus motacilla) are tail-waggers
extraordinaire. As a matter of fact, their genus name is from the Classic
Greek seio "to wave" and oura "tail." If
that wasn’t enough, motacilla is Latin for "moving
tail." Though we don’t get to see either very often here in
southeast Arizona, when we do that wiggling is usually the first thing
noticed.
Both are nearly always found close to water. The Northern is listed as a rare transient, with most records in May and August/September. Its normal migration range includes most of New Mexico, so it is one of our more common ‘eastern’ warblers. The Louisiana is listed as casual in fall and winter and one is found here nearly annually as a winter resident. The northern tip of its wintering range ends not far south of our area, and when one does visit, it is usually near permanent streams at mid-elevation ranges along the Mexican border.
These two birds are very similar in markings and habits. Both are largish warblers that are brown above, light with dark streaking below, have pinkish legs and a strong white supercilium. Differences are subtle, but observable. The infamous bobbing is more up and down in the Northern, and faster. The two clearly diagnostic differences are in the supercilium shape and flank color. The Louisiana’s supercilium is always white and broadens behind the eye, ending abruptly at the nape. That of the Northern is attenuated behind the eye and narrows to a point. It can be white to buff. Louisianas almost always have pale pinkish-buff flanks, contrasting with the background white of their underparts. The background color of the Northern’s underparts can range from white to sulphur yellow, but will not show differences in the flank area.
Other useful clues are that the throat of the Louisiana is white while the Northern usually has dark spotting or streaks. The streaking of the underparts is blacker on the Northern and more brownish on the Louisiana. Look for the white crescent underneath the eye. It is much bolder on the Louisiana.
Bill size differences are tricky. The Louisiana generally has a much larger bill, but Northern Waterthrushes breeding in their western range have longer (though not as heavy) bills and are of the whiter variety, compounding the problem for our area. Leg color can help a bit. Though both are pink, the Louisiana has the oft-noted "bubble-gum pink" legs while those of the Northern are browner.
Both have a sharp "chink" call note. The literature is somewhat confusing on telling them apart. They state that the Northern’s is not as loud and penetrating, and slightly sharper. The Louisiana’s is supposed to be higher pitched, richer, and not as hard as the Northern. Since either of these birds are a good find, my suggestion is to use the ‘chink’ note as a locator for the one you’ve gone to find after hearing about it on the hotline! Hope this helps. Good luck!
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This page was updated on 02/21/06