NORTHERN CALIFORNIA – The American Bittern’s “pumper-lunk” call has got to be one of the strangest sounds I have ever heard.
When I first heard it, I thought the sound was coming from some kind of oddball frog, but when I realized the sound was coming out of a bird, I was truly astonished.
Their calls, sometimes also referred to as “booming,” have given rise to the bird’s nicknames like “thunder pumper” and “water belcher.”
The call starts with the clapping of the bittern’s bill. As it claps, the bird draws air into its esophagus and holds it there.
Once the esophagus is sufficiently inflated, the bittern forces the air out past its syrinx (voice box) while pressing its head down and out. Think of it as something like a “melodious burp.”
You can see and hear a sample of the call in the video on this page, which was taken in April at the Sacramento National Wildlife Refuge in Glenn County, along the auto-tour route.
The call is used by males to establish their territory and attract females. They can hear challengers’ calls from more than 1,000 feet away, and respond by more booming, standing tall, and rushing out in a crouched position to meet challengers head on.
Usually, the battles between the males are relatively mild, consisting of more booming and posturing, but when the fights escalate, they can be brutal.
Male bitterns are known to fly up into the air and stab at each other with their sharp beaks until one of them leaves the disputed territory or simply cannot fight anymore.
Except for the breeding season when mating pairs come together, the bitterns live solitary lives in freshwater wetland areas that have high vegetation, like tules.
Camouflaged well by their brown and white bodies, they often stand stock still with their head held high, beak pointing skyward, so that the long brown streaks down their neck blend in with the shadows between the cattails and tules. It’s along the fringes of high vegetation where you’ll most likely see them, and usually in the early morning or dusk hours.
The bitterns’ eyes are yellow (except in the breeding season when they turn orange) and are able to cant downward, unlike most other birds whose eyes are fixed in their sockets and don’t move much.
This gives the bittern an advantage over some other marshland birds in seeking and finding prey. It’s also believed to rock its head back and forth when it’s hunting, so the eyes can see past the surface glare of the water into the depth below.
Like herons and egrets, bitterns hunt in and around shallow water with a stab-and-grab technique. They stand still, watching for prey, and then jab at with their bill when it comes close enough. Once caught the prey is either stabbed, crushed or shaken to death and then swallowed whole.
Bitterns have a varied diet that includes insects, crustaceans (crayfish are a favorite), fish, frogs and tadpoles, salamanders, snakes and small mammals like voles. What they can’t digest they vomit out later in pellet form (rather like owls do).
Between their fighting, belching, and vomiting male bitterns may not seem like much of a catch … and the fact that they only need about 15 seconds to mate may not impress ladies all that much, either.
But remember that these are generally solitary birds to begin with. The males depart as soon as the mating is over, and the female sets out on her own to lay her eggs and tend to her brood.
The female will pick out a spot among the cattails, sedges and tules that it can flatten out into a mound and then line with grass. Usually the mounds are around 15 inches in diameter, but they can be smaller.
She’ll lay a clutch of up to about seven eggs (that will be olive or beige-brown) and incubate them for about four weeks.
When the chicks hatch, they’re covered in pinkish-yellow down and sport a pink bill and large eyes (which like their parents’ can cant downward making them look cross-eyed a lot).
As soon as they’re able to lift their heads, they’re doing the bittern neck-stretch, pointing their bills at the sky, trying to blend into their surroundings.
They’re able to leave the nest in about two weeks, and fledge in about six weeks. By then they’re on their own: females looking for mates and nesting sites of their own, and males belching out their “pumper-lunk” calls to establish their territories.
Next time you’re out near a wetland area, listen for the American Bitterns. Their call is unmistakable and unforgettable.
Mary K. Hanson is a Certified California Naturalist, author and nature photographer. She will be co-teaching a naturalist course for the public through Tuleyome in early 2018. Tuleyome is a501(c)(3) nonprofit conservation organization based in Woodland, Calif. For more information, visit www.tuleyome.org.
Tuleyome Tales: The thunder pumper’s booming pumper-lunk call
- Mary K. Hanson
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