Dwellers of the Forest Floor


The life of the Swainson's warbler

In the dark recesses of the live oak forests floor lives a secretive dweller, a bird so hard to observe that nesting at Aransas National Wildlife Refuge wasn’t documented until 1988. This bird, the Swainson’s warbler (Limnothypis swainsonii) is often only detected by its garish, resounding song, given in the mid-level of a shady live oak forest. Swainson’s warblers also have a loud “chip” call which can attract attention to its location on the dark, forest floor. Certainly, the Swainson’s warbler plumage doesn’t match its bright song. An olive-brown colored bird about six inches long, the Swainson’s warbler can be identified by its pale eyebrow stripe and dark eye lores, its long bill, and pinkish legs. A ground lover, the Swainson’s warbler’s behavior of lifting and flipping leaves and small branches on the oak forest floor as it looks for insects and small spiders is quite unique for this species. In fact, they are much easier to hear than see, even when they may be only a few feet off the trail! And for the many birders and others who would love to find this mysterious species, learning its songs and calls, its behavior, and identifying its dull colors and field marks is the key to adding this bird to their life lists.

Swainson’s warblers were probably “discovered” by the artist-naturalist John Abbot in the early 1800’s likely near or in his home state of Georgia. But the bird’s secretive nature meant that few people actually observed this warbler very well in that early time period. In 1834, a warbler skin was obtained by John James Audubon from a specimen collected by a colleague of his, John Bachman of South Carolina. Audubon named the bird Swainson’s after a close naturalist friend from England, Willliam Swainson. The scientific name, Limnothypis swainsonii, reflects on the common name and it breeding range as well, since Limnothypis is defined as a denotation of marsh finch, because the bird was mostly reported living in swamps and floodplain forests. Indeed, Swainson’s warblers nest in hard to reach places in the southeast United States, often in canebrake and swamp forests, where many birders and researchers have trouble reaching. Perhaps at Aransas, this bird may be a tad easier to find, as it enjoys the leafy oak forests floor alongside wide open trails, although it still prefers areas with a thick understory of grape vines and saw palmettos. Swainson’s warblers can be found along a number of trails and open areas including both Birding Trails #1 and #2, the Big Tree Trail, the Fishing Pier wooded sections near the picnic tables, and even fairly close to the Visitor Center. Aransas NWR may be the most southern of the Texas nesting Swainson’s warblers as most others nest in the northeast section of the state.

These nondescript birds are neotropical migrants, nesting in the United States but wintering in the forests of the Yucatan Peninsula of Mexico, Guatemala and Belize and in the islands of the Caribbean and the Atlantic Ocean including the Bahamas, Cuba, Jamaica, Hispaniola, and Puerto Rico. The birds arrive in Texas from late March to mid-April and depart from late August through October. When nesting, the Swainson’s warbler will defend a territory from 7 acres to over 40 acres, which is a large territory for such a small bird. They create a nest that is cup-shaped and build from dried leaves, sticks and vines and placed near the ground in a small shrub or vine. The birds may conceal the nest with Spanish moss and other materials found in its location. From there they will lay normally two to five white, unmarked eggs, which is an unusual color for songbird eggs. After several weeks, the young, featherless chicks will hatch and remain at the nest for about one and a half weeks. After about four weeks and now feathered, the young will soon be on their own, although many fledged birds may remain with the parents for a longer time as they prepare to migrate south to more tropical regions.

If you are fortunate to observe this secretive denizen of the woodland stalking for bugs on a hot summer day, consider yourself lucky to be one of the few to watch this dweller of the forest floor in action. And stick around the woods, for other mysterious delights may be found in the realm of the live oak forest community.