Louisiana waterthrush  (Seiurus motacilla)

The Louisiana waterthrush is classified as Least Concern (LC) on the IUCN Red List (1).

An attractive bird with cryptically-coloured plumage, the Louisiana waterthrush (Sieurus motacilla) is renowned for its peculiar tail-wagging behaviour (3) (4) (5). This characteristic habit gave rise to the genus and species names of the Louisiana waterthrush, both of which mean ‘tail-wagger’, referring to the way in which the tail is constantly wagged in a distinctive teetering motion as it walks along the ground (3).

The forehead, crown, and upperparts of the Louisiana waterthrush are olive or olive-brown, with the wings and tail being mostly brown (4) (6). The underparts are white, with rows of grey-brown spots on the breast, sides and belly. The contrasting flanks and undertail-coverts are pale pinkish-buff, tawny or dull cinnamon (6) (7) (8). The throat is always bright white, but may have a few spots (8).

A pale grey line runs from the bill of the Louisiana waterthrush over the eye towards the neck, where it becomes bold white (4) (6) (8). A white arc may be seen under the eye (6). The bill often appears disproportionately long and thick given the relatively small size of the Louisiana waterthrush (8).

The male and female Louisiana waterthrush are very similar in appearance, with only slight differences in seasonal plumage (4) (6). This species has a loud, ringing, resonant song, comprised of rich, sharp, somewhat metallic notes (3) (8), which is described as a ‘sweeu-sweeu-sweeu-chee-ch-wit-it-chit-swee-you’ (6).

The breeding grounds of the Louisiana waterthrush are located in Ontario, Canada, and in the U.S., from Maine, Indiana, and Minnesota, west to Nebraska and Kansas, and south to Texas, Georgia and North Carolina (4) (9).

This species winters in the West Indies, Mexico, and in Central and South America (3) (9).

The Louisiana waterthrush prefers habitat that is near both water and forest. It generally occurs along open-banked, fast- or slow-moving streams with steep to moderate gradients, in forested watersheds or swampy areas with standing water (4) (5) (9) (10).

The Louisiana waterthrush typically avoids larger streams, perhaps because regular flooding associated with these areas may prevent successful nesting (10). It also appears to avoid polluted stream sites and fragmented woodland (9).

The Louisiana waterthrush forages primarily on the ground alongside streams (3), where it defends foraging territories (5). It feeds mainly on aquatic and flying insects, but beetles, ants, flies, and small crustaceans, as well as the occasional small fish, may be taken to supplement the diet in winter (5). During migration and on its wintering grounds, the Louisiana waterthrush tends to avoid forested wetlands, and instead forages along flooded roads or trails, and in parks, lawns and gardens (3).

This species begins to arrive at the breeding grounds in late March (9), and will often return to the same site each year to breed (5). The male Louisiana waterthrush usually arrives before the female to establish a territory, and will begin singing as part of a noisy courtship display to attract a mate (5). The male will continue to sing sporadically throughout the nesting period (5), often performing flight songs at dusk above the tree canopy (4) (5) (6).

The Louisiana waterthrush nests from late May to mid-June (5), with a single clutch of five white to creamy-white, spotted eggs produced per season (4) (5). A cavity nester, the Louisiana waterthrush builds a bulky nest in a bank, an upturned tree root, a hollow stump, or beneath fallen logs near running water, which is hidden by overhanging roots or grasses (5) (9). The male and female both construct the nest, which is built from wet, muddy leaves, pine needles, grass, and small twigs (5). The female Louisiana waterthrush incubates the eggs for 12 or 13 days. The fledging period lasts for 9 or 10 days, with both adults feeding the young for a further 4 weeks (5). 

Less common and widespread today than it was two centuries ago, the Louisiana waterthrush’s decline is mainly due to the reduction of suitable habitat, through clearing and channelization of streams, as well as pollution, and the impounding of rivers and streams to create reservoirs (10).

Additionally, because the Louisiana waterthrush is dependent on large areas of continuous forest (9), this species is likely to be threatened by increasing forest fragmentation. Timber harvesting, agriculture, urban development and gas drilling may further reduce the available habitat for this species (3).

In Canada, the Louisiana waterthrush has restricted and specialised habitat requirements on both its breeding and wintering grounds, making the population extremely sensitive to changes in habitat quality and quantity. Threats to the Canadian population of this species include reduced insect prey and reductions in water supply due to agricultural drainage, excessive irrigation and climate change, as well as logging and habitat fragmentation (11). 

Although there are very few conservation measures targeted specifically at the Louisiana waterthrush, the conservation organisation Partners in Flight (PIF) have included specific target population levels for this species in its regional management plans (2).

In Canada, a variety of legislative policies are in place in Ontario, providing some measure of protection to the specialised breeding habitat of this species. Furthermore, this species may afforded additional protection due to the steep-valley, streamside habitats where it occurs, as these areas are usually difficult to log, farm, or otherwise develop (11).

The Louisiana waterthrush would benefit from maintenance of its current habitat, including keeping streams clean and free off pollution, as well as by reducing forest fragmentation in wintering and breeding grounds (3).

Find out more about the Louisiana waterthrush:

1. BirdLife International - Louisiana waterthrush:
   http://www.birdlife.org/datazone/speciesfactsheet.php?id=9132
2. Cornell Lab of Ornithology, All About Birds - Louisiana waterthrush:
   http://www.allaboutbirds.org/guide/Louisiana_Waterthrush/id
3. Partners in Flight:
   http://www.partnersinflight.org/