This is a very shy bird, found in places where there are reeds. On the ground, it usually looks fairly compact as it wades slowly through the reeds looking for fish and amphibians. Bitterns will also eat reptiles, insects, and small mammals. In flight, it looks like a heron with a wing span of about 45 inches and a distinctive black pattern on the brown wings.

The nest is made in a well-hidden place a few inches above the water on a platform constructed from cattails, sticks, reeds, and grasses.

When bitterns are alarmed or waiting for prey, they stand very still with the neck straight up and the bill pointed skywards so that they are scarcely distinguishable from the surrounding reeds. They will even "sway in the breeze". Bitterns are noted for the loud booming call which males give in the mating season.