By Jeannie Marcure
This months’ feature bird might well be described as the “Mighty Mouse” of our local marshes and ponds. My memorable first encounter with this little dynamo occurred one spring day as my husband and I were carrying our kayak through a wet area to reach water. Alerted by a noisy chattering sound, we saw a small sparrow sized, brown bird perched on top of a nearby cattail, tail cocked and head thrown back in song. Far from shy, this little guy cooperated by standing his ground (or should I say cattail!) for several minutes and posing for a picture.
Later, when I checked my bird guides, I learned that I had just encountered a male Marsh Wren doing “just what comes naturally”— establishing and protecting his territory and looking for a mate. As the name implies, these diminutive birds are found exclusively in marshy areas with plentiful cattails and reeds.
In the Flathead, Marsh Wrens are migratory, arriving in April or May and leaving in late September or October. In the spring, the male arrives first and builds several “courtship nests” consisting of an oval outer shell of woven cattails and reeds which is anchored above the ground or water in vegetation. When the female arrives and pairs with the male she selects one of the nests and adds a lining of feathers and cattail down. Marsh Wrens are often polygynous with two to three females paired with one male. Extra nests may be used for roosting but in general probably act as decoys for predators. Some proof exists that females prefer the males who have the most nests on their territory, maybe because this skill serves as an indicator of his general abilities as a provider.
Despite the fact that they are only about 4 inches long and weigh only about 10 grams, male Marsh Wrens are extremely aggressive and often fight over territories until one has been forced to leave. They also decrease rivalry for food near their nest by destroying the eggs and nestlings of much larger birds such as Red Winged and Yellow-Headed Blackbirds. A few summers ago I was fortunate enough to observe a Marsh Wren chase a mink out of the cattails and into the water. Amazing behavior when you consider the difference in size.
According to The Sibley Guide to Bird Life and Behavior, the male and female Marsh Wren are very similar in appearance, but only the male sings and male juveniles learn the songs and can duplicate them by about 15 days of age. Remarkably, western Marsh Wrens know an average of 150 different songs and scientific research shows that they do not randomly pick songs from their repertoire but rather tend to follow a few specific patterns. Thus a male will move from song to song in a fairly predictable pattern. Males on neighboring territories often engage in matched counter-singing, the second offering up the song just given by his rival. Observers think that this behavior may reduce tensions between territorial neighbors.
The Marsh Wren feeds entirely on insects that it takes from plants as well as the surface of the water. It is typically a secretive bird, remaining well hidden in the cattails and reeds, briefly climbing a cattail for a look at an intruder; however I’ve found that in the early spring it’s fairly easy to spot the males by listening for their distinctive song or by listening for the rustling noise they make as they feed in the cattails.
Marsh Wrens can be found in the Flathead on most marshy ponds and lakes. My most reliable spots for sightings are at Smith Lake where they can readily be found in the cattails on either side of the boat launch area (no boat needed) and at Blanchard Lake where you’ll need to paddle along the cattails. Since I usually hear them before I see them, it may be useful to familiarize yourself with their sound before you heard out. If you have internet access there’s a good recording at: www.birds.cornell.edu/programs/AllAboutBirds/Guide/MarshWren