I AM told, on good authority, that bitterns used to live around Thirkleby Beck, a tiny stream running between the small villages of Great Thirkleby and Little Thirkleby, a few miles south-east of Thirsk.

The distinctive booming voices of the males could be heard on occasions even if the birds themselves were rarely seen.

I have no means of checking the veracity of this statement, nor do I know the period in which these rare birds were supposed to dwell in that area, but it is a fascinating thought, particularly as these birds are now so rare in this country and in this region in particular.

I have never set eyes on a bittern, nor have I ever heard its fabulous booming voice, but, to my knowledge, no bittern has been seen or heard in Thirkleby for a long, long time.

A bittern is a large bird which is related to herons and storks. Some 30 inches (one metre) long, it lives close to water in reed-covered or marshy areas and its colouring so closely matches the vegetation in which it lives and breeds that it is almost invisible to the naked eye.

With beautiful brown plumage streaked with black, brown and yellow, it is able to merge into the background with remarkable efficiency and, when it is alarmed, it stands motionless and stretches it neck skywards so that its markings resemble the surrounding reeds.

Rather than fly away, it will remain absolutely still until it believes the danger has passed.

When hunting its prey of frogs, small mammals and fish, insects or even tiny birds, the bittern moves around on foot among the reeds in what can only be described as a hunch-backed manner.

It rarely flies and seldom ventures willingly into open ground, always preferring the shelter of the dense reed beds.

It also nests among the reeds, building its thick nest on the ground by using vegetation and lining it with softer materials and then producing some four to six eggs in April or May.

So how did such a shy and secretive bird become so rare? The answer lies in its appeal as food for the human race. With the arrival of the shotgun, followed by drainage of many marshes which were its home, numbers began to dwindle alarmingly.

Unfortunately, many people regarded the bittern as a delicacy at table and this continued into the nineteenth century when special shoots were organised.

These were particularly effective in the fens and wetlands of eastern England where most of the nation's bitterns lived, but such shoots were also conducted in Wales, Ireland and the south of Scotland.

While the bittern had previously been considered plentiful, numbers plummeted quite suddenly and, by 1850, the bird had ceased to breed in the Norfolk marshlands. By 1868, it was no longer breeding anywhere in England.

Eventually, however, sanctuaries were created in places where bitterns could live in safety and peace and, although the birds lived in this country all the year round, we received visiting bitterns from overseas. They would arrive to spend the winter here, but some decided to remain and so, thanks to a combination of bittern welfare and some immigrants, our population of bitterns began to increase.

Just before the First World War, they had resumed breeding in England and, despite some severe winters and two world wars, their numbers increased steadily until the mid-Fifties.

Then they faced another extended set-back. This was chiefly due to the further widespread destruction of their habitat as more and more marshlands were drained and cleared. By 1996, only 11 breeding pairs were known in this country.

Since then, there has been an enormous effort to conserve the bittern, along with many other species considered to be under threat, and my latest information is that there are now about 30 breeding pairs in England.

Some of these are in special reserves, but it does seem that the conservation efforts are succeeding.

Although the sound of a male bittern is so distinctive and loud (it can be heard up to a mile away), I have never had the joy of hearing one.

The bittern's generic name is botaurus, which comes from the Latin boatum tauri, which means the bellowing of a bull.

That gives some indication of the sheer volume and distinctive sound which emerges from this bird's throat. In the spring, however, when it is mating, it is said the noise is more like the lowing of a cow.

The bittern also has a smaller and rarer cousin. This is the Little Bittern, with a black back and tan underparts, which is about half the size of the one described earlier.

It spends virtually all its time among reeds, only coming out at dusk, but this is really a visitor from Europe, Asia or North Africa.

Due to this bird's remarkable shyness, it is not known with certainty whether any are living permanently in England, but I will keep my ears and eyes open every time I pass through Thirkleby.

On the subject of birds, I have received an e-mail from a reader in Stanwick St John, near Richmond, who refers to the RSPB Garden Watch.

He tells me that there is a parallel organisation known by the initials BTO - the British Trust for Ornithology - which runs a continuous Garden Birdwatch operation with 15,000 participants.

While saying that the RSPB's annual bird watch is wonderful for raising an interest in birds among children, my correspondent feels it is not really very scientific.

In the case of the BTO, he tells me, each member formally reports every week on the birds seen in their gardens throughout the length and breadth of this country.

My correspondent adds that more volunteers are needed for the North, but nonetheless, this system is building a large and valuable database which helps to map the presence of birds in Britain during the entire year.

Aided by computers and a web site, members of the BTO can watch bird populations move week by week while knowing that whatever happens in a member's own garden is adding to the knowledge of about 50 of the most common species. I thank him for troubling to provide me with this information.

Following my notes about witches' broomsticks, I have come across a belief that witches would also ride around on coul-staves.

This word does not appear in my dialect dictionaries, but it is said to mean cabbage stumps, and there could be some linguistic link with cowls, these being the stems of heather.

A boddin o' cowls was the term used to describe an armful of stems cut from the heather, these being gathered for fire-lighting, and there is also a word "coulis", which refers to a thin sauce made from vegetables or fruit. Possible word associations?

So far as coul-staves were concerned, witches would grease these with the juices of either the wolf-bane, cinquefoil or smallage to make them easier to fly through the air and, if a cabbage stump was left in the ground to produce greens, it was customary to cut an X into the top.

This was said to ensure fruitfulness, but also to keep witches at bay and prevent them from spoiling the crop.

From this, there grew a belief that it was very risky indeed to serve cabbage as part of a wedding feast, although cabbage-water, saved after boiling a cabbage, was very good for easing blood pressure.

On the subject of dialect words and following my notes about owsing tins, I have heard from my Norwegian correspondent.

To refresh readers' memories, an owsing tin was a metal can with a long handle which was used to draw water from fireside boilers. The name comes from the Old Norse ausa, from which we get ouse, meaning water, also used as a name for some of our rivers.

My Norwegian reader tells me that owsing is still used in Norway and it means exactly the same as our dialect term. In addition, there is a similar term in Norway which is used to describe the baling of water from a boat.

And while chatting to me on the telephone, he also said that, in Norway, the term muck, with local spelling, is used to describe the mess left by cattle, although he has not come across our word plothery in Norway