Bird Files: Louisiana Waterthrush, Early Bird

May 23, 2014

The Louisiana Waterthrush nests in places where rocky streams riffle and run through dappled forests. In the olden days the Louisiana Waterthrush was called “water wood wagtail.” It does, indeed wag, or bob, its tail. This sleek, grey and white, sparrow-size bird is neither particularly common in Louisiana nor, technically, a thrush. It is a wood warbler, with a long pointed beak and a matching pointed tail. Pennsylvania, and other Appalachian states with forested streams, is home to an estimated 35,000 pairs of them for part of the year.

Louisiana Waterthrushes spend half of the year feeding along forested tropical streams in Mexico, Central America and the West Indies. They are among the very first Neotropical migrants to return to our region to nest each year, by the beginning of April. When they arrive, they begin feeding on a diet of stream insects, such as mayflies and stoneflies, known as irresistible bait for many kinds of fish. Some people have called the waterthrush a "feathered trout.” By the middle of May, when some migrant songbirds are only just returning to their breeding grounds, waterthrushes already are busy feeding their nestlings!

Waterthrushes can be inconspicuous as they hop along from rock to rock to log in a stream searching for food, all the while wagging their tails. But the male waterthrush's territorial song—swee-ut, swee-ut, swee-ut, tsit, tsay, twee-beo, tuwee—is one of the loudest of any warbler. It can easily be heard above the sounds of rushing water a half a football field away.

The Louisiana Waterthrush requires clean streams containing lots of natural food, so the species is a reliable indicator of stream water quality. Abandoned mine drainage, acid rain from industrial air pollution, agricultural runoff, and other resource extraction activities all can negatively impact the aquatic life in streams. When this happens, waterthrushes are affected, too: they’ll nest in smaller numbers, if at all, they’ll lay fewer eggs, and their young will grow more slowly.  Early coal miners knew how important it was to keep an eye on their canary in a cage: If the bird wasn't acting normal and healthy, the "environment" in the coal mine was unsafe for the miner, too. Wherever clean water rushes, there are waterthrushes; where there aren't, then people need to investigate what's wrong, because after all, we need clean water, too.

The next time you’re out in one of our county or state parks, maybe picnicking along a wooded stream, be sure to look and listen for the water wood wagtail, one of Pennsylvania's most interesting birds.

Bird calls from The Macaulay Library at the Cornell Lab of Ornithology, recorded by Curtis A. Marantz.