The Louisiana Waterthrush

The Louisiana Waterthrush 

Parkesia motacilla

 

The lovely, resonant song  of the Louisiana Waterthrush with its descending notes is one of the delightful indications that spring is really here.  The Waterthrush returns from wintering in Central America and the West Indies to look for nesting sites along relatively unpolluted headwater streams.   The male returns before the female and until he finds a mate he sings vigorously all day.  Once a mate is acquired his singing is predominantly in the morning.   The female also sings, though a shorter version of the song, as well as gives the same calls as the male.

The Louisiana Waterthrush is noted for constantly wagging its tail in a teetering motion as it forages.  Both the generic and specific name mean “tail-wagger”.

Louisiana Waterthrush populations and successful reproduction are decreased by the lack of benthic macroinvertebrates found in healthy streams and by the impact of acid rain on streams.  Thus this species is an indicator of a healthy ecosystem.

Preferred nesting sites are along fast flowing small steams, frequently at the headwaters of the streams.  Hence western Albemarle County is a good area to find them.  In upland forests the nest is usually placed in a cavity along a stream bank.  The male and female both walk along looking for the site.  The male will enter a potential site, turn around several times and drag nearby leaves into the cavity.   If the female does not enter, he follows her further up the stream to explore other sites.   Once she enters a site that is acceptable they both gather leaves from the immediate area to build the nest.   Once the nest is finished there is often a delay until the female begins laying one egg a day until 5 eggs are laid.  The eggs are approximately one third the mass of the female.  Incubation by the female begins the day before the last egg is laid and all of the eggs hatch the same day, after 10-14 days of incubation.  They leave the nest at 10 days of age.

The young are given the same food as the adults eat.  The predominate food consists of adult and immature stages of aquatic invertebrates.  They may forage along the forest floor, trails, and even in gardens and in trees if there is a shortage of food near their nest.

The brown-headed cowbird will frequently lay eggs in the Louisiana Waterthrush nest.  The adults will chase the cowbirds but if the cowbird is successful in laying in the nest the waterthrush may bury the alien egg under the floor of the nest, or peck, puncture and discard the cowbird eggs.   Since the eggs are similar in size and the cowbird will remove a host egg for each parasitic egg laid, sometimes the waterthrush will raise both species.  In some areas  studied cowbird parasitism led to a 50% reduction in fledglings of waterthrushes.

To  see a picture of and hear the song of the Louisiana Waterthrush go to:

http://www.allaboutbirds.org/guide/Louisiana_Waterthrush/id

and click on “Sound”

Submitted by Dorothy Tompkins

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