Birds
American Bittern
Botaurus lentiginosus · also called thunder pumper, stake driver, bog bull
You can stand at the edge of a marsh a few metres from an American bittern and never know it is there. The bird points its striped neck at the sky, sways with the reeds, and becomes part of the vegetation. Then, at dusk, it makes a sound like someone working an old water pump.
Overview
Botaurus lentiginosus is a stocky, warm-brown heron that lives alone and hidden in large freshwater marshes across North America. It hunts fish, frogs, and crayfish with a slow stalk and a sudden stab from the edge of the reeds.
The vanishing act
Alarmed, it points its bill straight up, draws its neck thin, and sways, lining up the vertical streaks on its throat with the reed stems until it disappears. It will hold this for a long time rather than fly.
The thunder pump
The male’s breeding call is a deep, three-part glug produced by gulping and expelling air, likened to a water pump or a stake being driven into mud. Because the bird is so hard to see, this boom is how anyone knows it is there.
Status
Least Concern globally but steadily declining, with heavy losses in the northeastern and midwestern US as big marshes are drained. Several states list it as endangered or of concern.
American Bittern: common questions
Why does the American bittern point its bill at the sky?
It is hiding. The bittern lives in reedbeds and cattail marsh, and its body is patterned with long vertical brown and buff streaks that match the standing dead and living stems around it. When a threat appears, the bird stretches its neck straight up, aligns those streaks with the vertical lines of the vegetation, compresses its outline, and often sways slowly as though the wind were moving it. A predator, or a birdwatcher, scanning the marsh sees more reeds. The bittern will hold the pose for a long time and only break it and fly, low and heavily, at the last moment.
What makes the booming sound in a marsh at night?
In much of North America, the deep, repeated, gulping thump heard over a marsh in spring is a male American bittern. The bird inflates its oesophagus with air using specialised muscles, then expels it in a slow, resonant, three-syllable call that has been compared to a water pump, a distant post being hammered, or a large bullfrog. It carries several hundred metres and is often given at dawn and dusk, sometimes at night. Because the bird is nearly impossible to see, this call is the main way people and researchers know a bittern is present.
How is an American bittern different from a night-heron or a juvenile heron?
An American bittern is a medium, chunky, warm-brown heron with heavy dark streaking down a pale throat and breast, a straight pointed yellowish bill, and a distinctive black stripe running down each side of the neck. It flies with quicker wingbeats than a large heron, showing dark outer wings that contrast with the browner body. A black-crowned night-heron is greyer and lacks the bold neck streaking, and immature herons and egrets are longer-necked and less richly striped. The bittern is also almost always alone and in cover, whereas night-herons and young herons are often in the open or in small groups.
Why is the American bittern declining if it is listed as Least Concern?
The global listing reflects that the bird still occupies a very large range across North America, so it is not at immediate risk of extinction. But long-term surveys show a steady downward trend, and the losses are concentrated where wetlands have been most heavily drained and broken up, especially the northeastern and midwestern United States and the southern Canadian prairies. The American bittern needs big, undisturbed, shallow marshes with thick vegetation, and it does poorly in the small, isolated, weedy wetlands that often remain. Several states and provinces list it as endangered, threatened, or of special concern even though the species as a whole is not.