Least Bittern Overview, All About Birds, Cornell Lab of Ornithology

Thanks to its habit of straddling reeds, the Least Bittern can feed in water that would be too deep for the wading strategy of other herons.

When alarmed, the Least Bittern freezes in place with its bill pointing up, turns its front and both eyes toward the source of alarm, and sometimes sways to resemble wind-blown marsh vegetation.

The Least Bittern and the American Bittern often occupy the same wetlands, but may have relatively little interaction because of differences in foraging habits, preferred prey, and timing of breeding cycles. The Least Bittern arrives on its breeding grounds about a month after the American Bittern, and leaves one or two months earlier.

John James Audubon noted that a young captive Least Bittern was able to walk with ease between two books standing 1.5 inches (4 cm) apart. When dead, the bird's body measured 2.25 inches (5.7 cm) across, indicating that it could compress its breadth to an extraordinary degree.