The furtive Least Bittern is often little more than a voice in the reeds that is frustratingly difficult to locate. But these diminutive herons reward patience and will charm birders persistent enough to discover them in their wetland haunts. They’re smartly clad in chestnut, buff, and black, with the male more richly colored than the female. Although drainage and development of wetlands has reduced their populations, Least Bitterns persist over much of their historical range, and are most readily seen during the breeding season.
Plan a dawn outing in May or June to a freshwater or brackish marsh, one with dense, tall vegetation like cattail or other reeds. Look for open-water areas—edges where the birds often hunt (and can be more easily seen). Walk slowly and pause to listen for the rapid, quiet coo-coo-coo-coo song of males. You might also see the birds as they fly from roosting to foraging sites, or returning to the nest with food. Not a morning person? Try watching in the same areas around dusk, when there is another peak of activity.
Other Names
Avetorillo Americano (Spanish)
Petit Blongios (French)
Backyard Tips
Least Bitterns won’t come to bird feeders—but a small created wetland in your yard can store, filter, and clean runoff water from your roof and yard and provide habitat for insects, amphibians, and birds, possibly including a shy migrating bittern. Habitat Network has more about creating water features in your yard.
When alarmed, the Least Bittern freezes in place with its bill pointing up, turns both eyes toward the source of alarm, and sometimes sways to resemble windblown marsh vegetation.
Perhaps surprisingly, tiny Least Bitterns use areas with deeper water than the much larger, longer-legged American Bittern. Least Bitterns can do this because their long, agile toes and curved claws allow them to grasp reeds and hunt small prey while suspended from these precarious over-water perches.
John James Audubon noted that a young captive Least Bittern was able to walk with ease in a 1.5-inch gap between two books, even though the bird's body normally measured 2.25 inches across—indicating that it could compress its body to an extraordinary degree to squeeze between marsh stems and reeds.
A very rare dark form of Least Bittern, known as “Cory’s Least Bittern,” was once considered a separate species. With a black bill, entirely black back, and rich chestnut cheeks, belly, and wing coverts, this distinctive bird was highly prized by bird “collectors” as soon as it was discovered in Florida in 1885. Cory’s Least Bitterns were seen frequently around the Great Lakes, especially around Toronto, in the late 1800s, before its favored marshes were destroyed. Only 7 or 8 records of this mysterious bird are known worldwide since 1973.
As in many other small herons, Least Bittern’s loral area (between bill and eye) is unfeathered, and this skin can change colors, depending on what the bird is doing. During courtship, copulation, or territorial conflict, the normally yellowish skin can flush brilliant cherry red in males—a sight worth watching for in spring and summer.
In some brackish marshes, notably in South Carolina, Least Bitterns may nest close to colonies of Boat-tailed Grackles, which typically choose areas without ground predators. The grackles also aggressively chase or mob hawks and gulls, another advantage for the bitterns.
Least Bitterns occasionally turn up far away from their usual range and habitat. In September 2007, for instance, a migrant was found at Vila do Porto, Azores, in the middle of the Atlantic Ocean.
Researchers tracked breeding Least Bitterns in western New York and found the birds used about 24 acres while feeding themselves and their offspring—about the area of 10 city blocks.
Herons
