The outside story: The elusive 'thunder-pumper'

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Often, when I spot an interesting bird, I don't have my binoculars handy. I'm holding a paddle or a pair of bicycle handlebars, which aren't very helpful when it comes to birdwatching. That was the case during an early-morning bike ride last summer, when I noticed a brownish bird about the size of a chicken standing at the edge of a farm pond. I would have liked a better look, but it was clearly an American bittern, scanning for prey against a backdrop of reeds and cattails.

It was a rare sighting for me, one I was lucky to have. It's typically harder to see this member of the heron family, since it is much more secretive than its kin. Living deep in the marshes, the American bittern blends in perfectly with the surrounding vegetation and maneuvers through the reeds by means of its laterally compressed body. When alarmed, it freezes in an upright position, its neck and yellow bill pointed skyward. Its marsh grass mimicry is so good it even sways with the breeze.

Having returned from their wintering grounds in the south, American bitterns have taken up residence in freshwater marshes. Cattail marshes are their preferred habitat, but they also turn up in reedy lakes, beaver ponds, and soggy fields. About ten inches shorter than a great blue heron, American bitterns have streaky brown and white plumage with black slashes on each side of their white throats. They feed while wading, snatching dragonflies, water striders, crayfish, frogs, and small fish and snakes.

Even if you don't spot this retiring, solitary bird, you might hear it. The male's low-frequency breeding call carries far across the marsh. Most often heard at dawn or dusk, it starts out like the sound of someone whacking a stake into the mud. The bird then inflates its esophagus and, raising and lowering its head, releases a hollow pumping sound that has been compared with the sound of a bellowing bull, the loud gulps of a giant, and an old-fashioned washing machine on its last legs. It's often described phonetically as "onk-ka-chonk!" or "pump-er-lunk!" - although it utters a hoarse "kok-kok-kok" in flight. Its unusual call has led to a raft of common names, including thunder-pumper, water-belcher, mire-drum, booming bittern, Indian hen, bog bull, meadow hen and stake driver.

As nearly invisible as bitterns are, it's rare to witness their breeding behavior. Paul A. Johnsgard observed courtship twice: in the 1970s in Wyoming, and in 2015 in North Dakota. He is a renowned ornithologist in his late 80s, the author of more than 50 books on birds, so you wouldn't think much could surprise him. However, he said when I reached him in his University of Nebraska office, "I almost literally gasped. Looking like something out of `The Wizard of Oz,' the male slowly raised two snowy white, fan-shaped clusters of feathers from the scapular feathers in front of its wings. It was like an extra pair of small white wings that you'd never see on the bird at any other time. It was almost hypnotic. He did this for about 15 minutes, trying to advance on the female about 20 yards away."

One of the most avid local birders I know has looked for bitterns many times without success. Another has seen them in Texas and Florida, but not the Northeast. However, landscape and bird painter Cindy House has seen many in the Sunapee Region of New Hampshire while scouting for subjects — and once witnessed the exact behavior described by Johnsgard.

North America has just one other kind of bittern: the least bittern, which is a species of high conservation concern in the Northeast. This is the smallest North American heron, about the size of a mourning dove. Its colors are more striking than those of its larger cousin, and it inhabits deeper marshes. It's not a boomer; its call is a soft "coo-coo-coo." The least bittern weighs a mere three ounces, and often hunts while grasping reed stalks with its toes and leaning down to the water surface. It's hard to picture the nine-day-old chick of a bird so small, but that is the age at which least bittern chicks leave the nest.

I have yet to see a least bittern, but I'll be on the lookout. Next time I go scouting, though, I might try a kayak instead of a bike.

Laurie D. Morrissey is a writer in Hopkinton, New Hampshire. The Outside Story is assigned and edited by Northern Woodlands magazine (www.northernwoodlands.org) and sponsored by the Wellborn Ecology Fund of the New Hampshire Charitable Foundation (wellborn@nhcf.org).

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