Listen for the strange evening song of an elusive summer visitor

Perhaps it should not be described as a song because it is rather tuneless and monotonous, being little more than a churring sound, usually heard at night. Some have described it as being like the noise of a tiny motor being revved for periods of about five minutes and then being allowed to idle, only to be revved again. The system is repeated with a corresponding rise and fall in the pitch of the notes.

However, the bird which is often called the churn owl is not an owl. It is the nightjar, its name coming from the sound of its voice and the fact it flies at dusk during its insect-hunting activities. It has other names too. In some parts of the Midlands, it is called the lych fowl, while in areas of the South it was known as the puck bird, and in Spain it was once known as the shepherd's deceiver.

These names arise from ancient superstitions which were associated with this peculiar bird. Some believed it to be in league with the devil, probably due to its night-time activities, and it was thought to suckle goats, sheep and cattle. It was also blamed for spreading disease and blindness among humans, while in some areas it was associated with death and corpses. That is why it is called the lych fowl. It was also thought to be a witch because it flew at night in silence, and some believed it could be killed only with a silver sixpence fired from a gun.

With this kind of reputation, none of which was true, it is not surprising the bird was regarded with more than a hint of distaste and even fear, but in these modern times we are not superstitious and bird-watchers spend a good deal of time trying to catch sight of nightjars during late summer evenings. They do so out of interest, and without any intention of shooting them with silver sixpences!

Nightjars are summer visitors to these islands, arriving in the spring and remaining until October, being most often seen along the east of the country and in the south. They do visit this region, however, and can sometimes be seen and heard in Dalby Forest near Pickering.

Slightly larger than a blackbird, the nightjar has beautifully mottled plumage in a range of colours including reddish-brown, grey, black and white. This makes it almost invisible among its surrounding as it spends its days squatting on the ground. It can sometimes be mistaken for a length of dead wood or pile of dead leaves.

The nightjar also nests on the ground, laying only two eggs, and when sitting on the nest the parent birds are almost invisible. Both male and female share the task of incubation, the hen sitting during the daytime hours with both helping to feed the youngsters. If there is a second clutch, the male will usually care for the brood.

Sometimes the nightjar will roost in a tree, in which case it sits lengthways upon the branch. This makes it difficult to see and then at night these birds take to the skies in their search for insects. Even though the nightjar's beak is small, it opens into a huge gaping mouth bordered by small hairs which enables it to catch insects such as moths while on the wing.

In flight, the wings look scimitar-shaped, rather like those of a swift, and the tail is spread wide with a blunt end. A silhouette of this shape is probably the only sight of a nightjar that most of us will catch and, as the bird is not at all common, we might be forgiven for not recognising it.

Continuing the topic of summer visiting birds, I have received a fascinating letter from a 99-year-old reader who lives in Leyburn. She relates a unique experience involving a cuckoo and reminds me of one of the verses associated with this bird, although she cannot recall the entire poem.

It goes: "The cuckoo is a pretty bird, it singeth as it flies; It bringeth us good tidings and telleth us no lies; It sucketh all sweet flowers to maketh its voice clear; And never singeth 'cuckoo' until the summer's near; The cuckoo is a witty bird, no other is as she; A nest she never buildeth....

My correspondent does not know the final line or lines and none of my sources contain them, although the first portion of this verse does vary from place to place. In some versions, the female bird is featured, while others refer to the male.

My correspondent relates a story which she and her husband experienced more than 60 years ago near Doncaster. They saw a female cuckoo drop like a stone into a hedge at the roadside. A minute later, she flew off and when my correspondent examined the hedge, she found a dunnock's nest containing a warm egg. It was larger than the dunnock's single egg already in the nest.

In the days which followed, the pair kept a close watch on the nest, even to the extent of watching the naked young cuckoo emerge from its shell to shoulder the remaining single dunnock egg out of the nest.

The dunnock, also known as the hedge-sparrow, then fed the ugly, yellow-mouthed invader until it was fully fledged and twice the size of its foster mother.

Finally, they saw the cuckoo fly away. It was an experience my correspondent has never forgotten, and which she has described so beautifully in her well-written letter.

Another remarkable letter comes from an 83-year-old reader at Brompton, near Northallerton, in which she vividly describes her childhood years at Carperby in Wensleydale.

She refers to some of my earlier notes in which I referred to the rabbit warren at Lady Hill and can recall the silvery-blue rabbits which were bred there.

Apart from supplying food and clothing in the distant past, she recalls these rabbits' fur being exported to Russia to make hats for the Tsar and suggests the warren might have been created long ago by the estate of Bolton Castle. This was done by some large landowners to keep the estate and its workers in food and clothing.

She also remembers playing in the woods above Aysgarth Station when she was a very small girl. In the woods was an old tumbledown shed with a fence around it, and her two elder brothers warned her about going near it.

They scared her off by saying "Ginny Greenteeth will get you!" At that time, she thought Ginny Greenteeth was a figment of her brothers' imagination and was very surprised to read my account of a river sprite of that name.

Jenny Greenteeth was supposed to be an evil sprite which haunted northern rivers to drag in and drown those people or children who wandered too close to the water's edge. The Tees also had such a sprite, this one being called Peg Powler, who operated in the stretch near Piercebridge.

My correspondent's memories of Wensleydale include explorations near the River Ure. She recalls the thundering of Aysgarth Falls when the river was in flood and, in her words, "the stupendous silence one year when they were frozen solid." At the time, she would be seven or eight years old.

I thank both my articulate senior correspondents. Their letters are a lesson to those who now permit youngsters to leave our primary schools without being able to read, write and spell correctly.

I have come across a curious custom which was once very common in the district around Northallerton. I believe it died out about 1800, but until that time it was common practice for young men, and perhaps some young women, to visit a surgeon to be bled. This was done in the springtime and the practice was thought to ensure good and vigorous health. The cost of this medicinal bleeding was a shilling (5p) and it seems the surgeons of the time made a handsome income from the practice.

This odd ritual might have had ancient links with the belief that a witch's harmful charm might be broken if blood was drawn from the victim. This would seem to match the Northallerton idea that being bled ensured good health.