Wednesday, August 20, 2014

Northern Waterthrush vs. Louisiana Waterthrush

An unexpected wave of migrants greeted us in the nets this morning with 69 new birds and 7 recaptures of 12 different species.  Prairie Warblers were out in force with 28 of them banded.  It is looking like a good year for them as we have already banded more than half the total from last fall in the first 6 days of the season.  Other notable species include first-of-the-season Willow Flycatcher, Black-throated Blue Warbler, and Worm-eating Warbler.

We captured a decent number of Northern Waterthrushes today and I as able to capture an okay photo of one so that I can explain some of the differences between Northern Waterthrushes and Louisiana Waterthrushes.  The most obvious field mark in separating the two is the color of the supercilium (eye-stripe).  In Northern Waterthrushes the supercilium is narrow and yellowish while the Louisiana Waterthrush has a broad, white supercilium.  Notice in the photos below that the Louisiana Waterthrush's supercilium is about as wide as the Northern Waterthrushes and but is a little whiter in color.

Northern Waterthrush from 08/20/14

Louisiana Waterthrush from 08/17/14
 Another area that we look at is in the throat.  Northern Waterthushes have a speckled throat opposed to the unspeckled throat of the Louisiana Waterthrush.

Northern Waterthush:  note the speckled throat

Louisiana Waterthrush:  note the lack of markings on the throat
A third characteristic that is not visible in the field is the pattern of the undertail coverts.  Northern Waterthrushes have a dark bases with lighter tips while the undertail coverts of Louisiana Waterthrushes largely unmarked or with a pale gray center.

Undertail coverts of a Northern Waterthrush

Undertail coverts of a Louisiana Waterthrush
A final characteristic that is sort of visible if you compare the first two photos is the length of the bill from the nares to the tip.  Louisiana Waterthushes  on average have larger bills (10.2-12.2mm) than Northern Waterthrushes (9.0-10.7mm).


1 Willow Flycatcher
11 Red-eyed Vireo
1 Carolina Wren
1 Worming-eating Warbler
5 Northern Waterthrush
1 Black-and-White Warbler
9 American Redstart
4 Yellow Warbler
1 Black-throated Blue Warbler
28 Prairie Warbler
7 Painted Bunting

1 Prairie Warbler
3 Northern Cardinal
3 Painted Bunting

# of Birds Banded:  69
# of Recaptures:  7
# of Species:  12
Effort:  118.0 net-hours
Capture Rate:  64.4 birds/100 net-hours
# of Nets:  20

Aaron Given
Mattie VandenBoom
Libby Natola
Matt Zak


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