AMERICAN BITTERN by Glynnis Thomas

Birds of the Month | March 7, 2018
AMERICAN BITTERN by Glynnis Thomas

Here’s the difference between the American Bittern (Botaurus lentiginosus) and its European counterpart the (Great) Bittern (Botaurus stellaris), and I’m not talking about description (there are some superficial plumage differences), or size (the Great Bittern is slightly larger). No, I’m talking about life-style.

In winter, the American Bittern has it easy. It comes down from the northern states to bask in the sunshine and winter warmth of the Gulf states, and best of all – Florida! The (Great) Bittern on the other hand comes down from Scandinavia, Russia and the icy steppes of northern Europe to spend the winter in southern Europe and the UK. Here it tucks down and conceals itself in cold, wintry reed beds and marshes, occasionally rousing itsself to fly across the reed tops from one area to another.

Here’s the difference between the wintering American birder and his European counterpart. The American birder in T-shirts, sandals and shorts (or probably his lightweight birding clothes), casually lounging on the boardwalk, takes endless pictures of the American Bittern situated in the reeds an arm’s length away. Occasionally another bittern flies across and lands in the reeds somewhere else, but it hardly raises a gasp. We are not thrilled unless it is close by.

The British counterpart sits in an ill-constructed hide, casting baleful glances at newcomers who open the door and let in an icy blast of wind. She sits for hours with patience and fortitude, her fingers nearly dropping off despite thick gloves and hand warmers. If she’s lucky she’ll just catch a glimpse of a distant bittern as it rises from one spot in the reed bed about half a mile away and plonks down again not far away. She crows with joy! A nemesis bird for some time, this was my life bittern experience. After waiting in a freezing, uncomfortable hide for several hours I was rewarded in the aforesaid manner by the sight of a bittern briefly rising from the reeds, flying a short distance and disappearing again into the reeds not to be seen again. But I had my mysterious, enigmatic, shy, secretive, almost impossible-to-see BITTERN!

This was in contrast to my first American Bittern, viewed at the edge of a small pond, through a telescope, creeping along in slow motion, creeping, creeping along and feeding along the reedy edge. At times one foot raised and held as if frozen before slowly, comically, setting it down again. We had it in the scope for a long time, watching its slow precise movements along the edge of the reeds, at times disappearing, melting into the reeds and freezing there, totally merged with the reeds, so you could no longer see where bittern ended and reeds began. Blink, and you’d have lost it.

And it is just this skulking, secretive, solitary nature which lends the American Bittern, along with its family, its appeal. That and its ability to stand motionless for long periods of time. Recently I observed a bird that was so still that when it fixed its eyes on a prey and slowly moved its head towards it I could hardly detect any movement at all until its final lethal lightning strike. Only when I looked at the photos later could I see the minute differences which recorded the imperceptibly slow movement of the birds head.

Predominantly nocturnal the bittern lives a secretive life amidst dense vegetation, relying on its loud calls to announce its presence, and on its hearing to detect the presence of others. In flight its call is a single or repeated deep and hoarse ‘graoh’. But it is the male mating call, the ‘boom’, for which it is known.

Because of its secretive and skulking nature it was long unclear exactly how the Bittern produced its distinctive booming call. A mediaeval theory held that the bittern thrust its beak into the boggy ground of the marsh in which it lived, making its vocalization which was amplified and deepened as it reverberated through the water. A reference to this theory appears in 1466 in Chaucer’s The Wife of Bath’s Tale:

And, as a bitore bombleth in the myre,

She leyde hir mouth un-to the water down

It has since been discovered that unlike most other birds which rely on the syrinx (or voice box) to make their presence known, the male bittern’s remarkably loud and booming mating call is made by gulping down air into its very long oesophagus and then releasing it in a booming belch, effectively turning its gullet into one great echo chamber. The boom call of this species is invariably described as resembling the noise of an old fashioned hand pump, or of hammering a stake into muddy ground, leading to two of the bird’s nicknames – ‘thunder pumper’ and ‘stake-driver’.

At 101 decibels the bird can be heard up to 3 miles away, 101 decibels being equivalent to a chain saw, pneumatic drill, jackhammer or speeding express train. But it is not only the volume of the call but also its quality of resonance and penetration that make it so far reaching. Incidentally the deep booming of the bittern has been measured in hertz – the number of sound waves going by at any one time, usually expressed in terms of thousands of hertz, or kilohertz (kHz). A bittern’s boom clocks in at around 200 cycles per second or 200 hertz. In contrast, and at the other end of the range, a kinglet sings at a frequency of around 9,000 hertz or 9 kHz. These two sounds pretty much cover the entire span of sound frequencies uttered by birds, low frequency sounds carrying further than high frequency.

Obviously this sound is only heard on the bittern’s breeding ground and my guess is that few of us have heard it. But what a fascinating bird this is. I still can’t quite get over how accessible this bird is here in Sarasota compared to the UK. Another great reason to be a SAS member and spend the winter in sunny Florida!