How to find American and Least Bitterns

I knew that I was looking at a bird. I saw it creep out to the edge of the cattail thicket.

That is, I watched yellow-green legs and spindly toes moving, and I saw disembodied golden eyes watching me, and I knew that they belonged to the same animal, an American Bittern.

In between legs and eyes, there had to be a stocky body and a long, tapered neck covered in beautifully streaked white and chestnut feathers.

But where?

I slowly lowered into a crouch in an attempt to get a better angle. The action caused the bird to freeze. For a second, the outline of the bittern, caught in mid-step at the edge of a small channel within the vast marshlands of Klamath Lake, Oregon, was clearly visible.

Then the bird changed position as well, drawing itself up into a spire-like posture, the celebrated cryptic stance of its kind. In an instant, the streaks on its neck blended flawlessly into the background of cattails, and I found myself once again staring into eyes without an owner. We stayed motionless for a time — me squatting, the bittern standing tall and gently swaying back and forth in time with the reeds.

After a few minutes, however, the bird contracted into a hunched position similar to my own and began opening and closing its bill, accompanied by soft gulping breaths. Its body swelled like a feathered dirigible as it did so, a huge bulge growing from its neck and chest. Then, about the time I expected the ballooning bird to burst in a puff of feathers, a deep pumping rhythm began resonating from its chest, punctuated by claps of the bill. The neck moved like a piston, creating the pulsing boom that has earned the bird the folk names thunder pumper, sky-gazer, stake driver, and mire drum. The call echoed across the water.

When the bittern finally completed its performance, it quickly deflated and slunk back into the cattails, disappearing from view. Amazed, I sat trying to comprehend what I had just witnessed. It’s not every day that a birdwatcher gets to observe a bittern, one of our shyest birds, and it’s rarer still to get to watch one give a full breeding call. For most of us, it’s a once-in-a-lifetime occurrence.

But it doesn’t have to be.

In a good location at the right time, and armed with the right information, you can see bitterns more easily than you might think. That’s what I learned from ornithologists James P. Gibbs and Guy A. Baldassarre, professors and bittern researchers at the College of Environmental Science and Forestry at State University of New York. Their insights, gained from years of experience and study, form the basis of the bittern-finding advice contained in this article.

Very different birds

Two species of bittern are found regularly in North America: the American Bittern and the much smaller Least Bittern. Gibbs believes that one of the greatest mistakes bittern watchers make is ignoring the differences between the two. “These are very different birds,” he says, “and many people treat them as though they are different versions of the same animal. People fail to see bitterns simply because they are looking for the wrong bird in the wrong place at the wrong time.”

The most obvious difference, and one with a huge impact on their behavior, is the size of the birds. American Bitterns measure 24-33 inches from bill tip to tail tip, while Leasts are only 11-14 inches long. The difference clearly makes formulating a one-size-fits-all search pattern tricky. One species is large and stocky, and the other is smaller than some rails.

To help you remember the sizes you’re looking for, try comparing them to more conspicuous species: American Bitterns are about the size of a Snowy Egret; Leasts are smaller than Green Herons and close to the size of a Mourning Dove. It sounds simple, but this mental calibration can keep you from passing over birds while scanning likely habitat.

Bitterns are well known as inhabitants of marshes, and the two species often occupy different areas within the same wetland. The bigger Americans require much larger territories to survive than do Leasts, so they are tied to extensive wetlands or large networks of smaller marshes. Leasts reach their highest densities in expansive habitats but can be present in nearly any size of wetland within their range. Protected areas generally house the largest tracts of marsh, so a refuge, wildlife management area, or other large marshland is the best place to begin your search.

Within the wetland, bitterns will focus on edges, places where habitat types change abruptly. Leasts are nearly always seen gripping reeds at the interface between open water and vegetation, close to the surface of the water. Americans prefer to wade, not cling. Most often, they stick to openings and channels in the marsh where the water is shallow enough to negotiate on foot.

Neither bittern will be found far from dense cover, to which they will retreat if threatened. Look especially for dense thickets of cattails, reeds, grasses, or any other vertical cover. Tangles of shrubbery and scrub are more difficult for bitterns to move through and don’t tend to attract them. Their preference is apparent in their plumage: The long stripes running down their necks work like camouflage. They help the birds melt seamlessly into the habitat.

In any marsh, the easiest way to tell if bitterns are present is by their calls. The booming of American Bitterns is easy to recognize and can be heard from great distances. Least Bitterns give a distinctive, muffled chuckling call.

It always helps to familiarize yourself with the songs of your quarry before heading into the field, and doing so can be as simple as listening to a recording during the drive to the marsh.

The calls are reassuring signs that bitterns are present, but keep in mind that not every bird will call, and that the bitterns’ repertoire also includes a variety of surprising noises that you may not recognize. For example, when flushed, Americans may give a hoarse kok-kok-kok, while Leasts may emit a shrieking quoh. In addition, you are much more likely to hear calling on days with little wind, and at specific times of day. Listen for Leasts especially at dawn and dusk, and for Americans at dusk or night.

Seasonal timing

While detecting the right habitat and calls is important, perhaps the most crucial component of a successful bittern search is seasonal timing.

In parts of North America — along the Pacific coast, in extreme southern California, along the Texas coast, in southern Florida, and in the mid-Atlantic — one or both bitterns occur year-round. In such locations, the sparser cover in winter can make for easier sightings. Bitterns are most conspicuous, however, on their breeding grounds, as this is where they will be doing most of their calling and foraging.

Least Bitterns breed in North, Central, and South America. The subspecies that occurs in North America (the nominate subspecies exilis) breeds primarily in the southeastern part of the continent. American Bitterns breed farther north and over a larger portion of the continent. Their range reaches from coast to coast and from Great Slave Lake and Newfoundland south to the central United States.

Given bitterns’ extremely cryptic nature, researchers are just beginning to understand the birds’ movement patterns. “What we’ve found is that American Bitterns generally reach their breeding grounds from early March to April, and Leasts tend to arrive a month or two after that,” advises Gibbs.

“The best time to hear them calling,” he says, “is in the first two months after they show up. After that, calling tends to taper off as their focus moves towards breeding.”

In order to ensure that you hit this window, time your trips around early to mid-May, when it is most likely that both bitterns will be present and (hopefully) calling.

If you hear calling at your location but don’t see a bird, don’t give up. The best time for laying eyes on a bittern is once they have begun to raise their families.

“During brood-rearing is an especially good time to see bitterns,” explains Baldassarre. “As the breeding season progresses, the demand for food for their chicks increases, and you often see bitterns in flight as they move between foraging grounds and their nest.”

To capitalize on this opportunity, make sure that you are at the marsh early in the morning or late in the afternoon, when the birds will be making their commutes. Late June tends to be the best time to catch both species in brood-rearing, as the Americans are in the middle of rearing, and the Leasts are just getting into full swing.

One last dilemma confronts bittern watchers: How can you visit a bittern’s world without harming the habitat or stressing the bird (and the birdwatcher, for that matter)?

Bitterns reside in the heart of the marsh, but trails in many refuges follow dikes and higher grounds that ring the outer perimeter. Slogging through the marsh is an obvious no-go. Doing so will damage the wetland and disturb its inhabitants, and it’s far from stealthy. What’s more, birders who go wading run the risk of getting hopelessly stuck. The solution is quite possibly the most underrated and underused practice for wetland birding — birding by boat.

Canoes, kayaks, and small inflatable rafts are invaluable tools for finding bitterns. They allow access to pristine areas where birds will be less wary of humans, more abundant, and much more approachable. Canoes and kayaks especially can be nearly silent and cause little or no damage, perfect traits to avoid alarming secretive birds. Your best bet is to paddle slowly through quiet channels in reedy or grassy vegetation, watching for bitterns where water meets reeds. Least Bitterns are a bit more curious than Americans and may even come out to get a look at you as you glide by.

Patience and persistence

If you must remain on land, patience and persistence are your best tools. Find trails or boardwalks that weave through cattails or other reeds, and once you find a channel or opening, have a seat. Bitterns freeze as an immediate response to danger. The more you move, the less they will. By staying put, you increase your odds of picking up on slight movements that will betray the bird’s presence and decrease your chances of walking right past the bird you’re looking for.

Looking for bitterns can be frustrating, so much so, at times, that a birder might consider trying to flush birds or disrupt their activities in order to gain a sighting. Steer clear of such tactics. Bitterns’ shy nature makes them sensitive to harassment, and flushing exposes birds to predators. Broadcasting recorded bird calls is prohibited in protected areas and will likely have the opposite of the desired effect, anyway. Rather than approach the source of recordings, bitterns often quickly move away.

And don’t forget: your own comfort is important, too. Marshes are great places for birds because they are also great places for insects. On bittern-breeding wetlands, mosquitoes can be intense, and they are particularly active during the best times for bittern watching. A healthy supply of bug repellant can make an evening’s birding a lot more pleasant.

After all, you wouldn’t want a mosquito to keep you from seeing a pair of ghostly yellow eyes with a mysterious owner, a species that even seasoned birders spot only irregularly, or better yet, from enjoying a once-in-a-lifetime performance by a thunder pumper.

Chris Duke is a nature writer based in Seattle who has worked as a wildlife biologist for the World Parrot Trust in Bolivia. He wrote about finding Oporornis warblers in our June 2009 issue and Catharus thrushes in our October 2009 issue. He thanks James P. Gibbs and Guy A. Baldassarre, whose experience and help were invaluable for this article.

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Originally Published December 28, 2009