Underground flying squad
QUESTION Do any birds nest in burrows?
THE Atlantic puffin and Manx shearwater excavate and nest in burrows.
each summer, 120,000 Manx shearwaters — black and white birds with long, stiff wings — visit Skomer, an island off Pembrokeshire, to breed in the burrows that riddle the landscape.
A pair flies for thousands of miles to return to the same burrow and raise one fluffy chick a year. To avoid predator gulls, the parents wait until the cover of darkness before heading out to fish.
Shearwater chicks become so big they are unable to leave the nest — they must go on a crash diet in preparation for their journey to South America for winter.
The Manx shearwater’s scientific name is Puffinus puffinus, yet it is not related to the puffin. It’s a tubenose, a group that includes fulmar, giant albatrosses and storm petrels.
Puffin is an Anglo-Norman word (Middle english pophyn) for the cured carcasses of nestling shearwaters.
The Atlantic puffin ( Fratercula arctica) acquired the name later, probably because of its similar nesting habits. They are members of the auk family, more closely related to guillemots.
The Atlantic puffin spends autumn and winter in the cold northern seas before returning to coastal areas around Scilly and Cornwall for the breeding season in late spring.
Between 100 and 200 pairs nest in clifftop colonies, digging a burrow in which a single egg is laid. After six weeks, the chicks are fledged and make their way to the sea. They do not return to land for several years.
Frances Bradshaw, Lowestoft, Suffolk. The burrowing owl, found in North and South America, lives in open grassland and deserts. It often nests in burrows made by ground squirrels, though it can dig its own. If threatened underground, it will make a sound like a rattlesnake.
Several will often be seen looking in the same direction like a family of meerkats. If chased, rather than fly, they run away on their long legs.
Found in parks, airports and golf courses, their low living habit mean many are killed crossing roads. One can be seen in Norfolk, happily burrowing away at Cromer’s Amazonian zoo.
Dave Warner, Fleckney, Leics.
QUESTION With today’s technically designed golf clubs, how would a smooth golf ball react when hit?
IT WOULDN’T go as far as a dimpled golf ball. The dimples are there for aerodynamic reasons.
The first golf balls were smooth, but after being struck repeatedly, they became covered with small dents. Golfers noticed it was possible to hit an old, battered golf ball significantly further than a smooth new one.
wind tunnel tests found that at 150 mph, the speed they usually travel at, a roughened golf ball produced less drag compared to a smooth one. dimpled golf balls were first manufactured in 1930.
when air flows at speed over a smooth golf ball, the thin layer of air next to the surface slows down, forming a boundary layer. when this slow-moving layer nears the point of maximum diameter, it tends to break away from the surface. This leaves a turbulent wake behind the ball, causing drag that makes it slow down.
dimples cause local turbulence in the boundary layer so it is re- energised by the faster moving air around the ball. This faster boundary layer sticks to the surface longer, resulting in a smaller turbulent wake, halving the drag and doubling the distance the ball will fly. If a ball had a small number of large, deep dimples, the extra drag would outweigh the benefit of the reduced wake diameter. lots of small dimples would approximate to a smooth sphere and not produce any benefit. The optimum number is between 300 and 500.
If the ball is spinning in flight, the dimples help drag the airflow around it to generate a force at right angles to the direction of flight. Backspin creates a lifting force and the ball flies further. If the ball is spinning about its vertical axis, it will veer to one side.
Denis Sharp, Littlehampton, W. Sussex.
QUESTION Did Wedgwood have European competitors in its heyday?
WEDGWOOD’S chief competitors in the 18th and 19th centuries were the royal ceramics houses of Meissen in Germany, Sevres in France and Royal Copenhagen in denmark.
wedgwood was founded in 1759 in Burslem, now part of Stoke-on-Trent, by Josiah wedgwood, who invented Jasper, Queen’s ware and Black Basalt.
Meissen had been founded in 1710 to exploit the newly discovered formula for white porcelain, until then a secret known only in China and Japan.
Saxony elector and Polish king Augustus the Strong was a porcelain fanatic who had imprisoned alchemist Johann Friedrich Bottger until he had come up with the formula, which then revolutionised the market worldwide.
To signify its authenticity, the crossed swords trademark was introduced in 1722. Meissen’s porcelain reflected the influence of eastern Asian art, depicting stylised plants and animals. It remains a powerhouse in the ceramics world.
French porcelain was produced at Chantilly, St Cloud and Vincennes from 1738 and enjoyed financial support from louis XV and Madame de Pompadour. By 1756, a new factory on the edge of Sevres was noted for its blue lapis colouring.
danish chemist Frantz heinrich Müller founded the Royal Copenhagen factory in 1775.
Blue fluted plain — a delicate, handpainted cobalt blue floral pattern imprinted on white porcelain — was the first dinnerware pattern produced by the factory and is still in production.
Sarah Waterhouse, Kenilworth, Warks.
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