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).