Flying into old age . . .
QUESTION Further to Britain’s most popular birds (Mail) — robin, barn owl, blackbird and the others — what is the average lifespan for these species. And which British bird has the longest lifespan? The problem with defining average lifespan in birds is that first-year mortality is high, mainly because of starvation and predation, so it tends to be very low, especially in smaller birds. So when lifespan data is given, it is usually accompanied by longevity data (i.e. longest lived).
These types of statistics are collected via ringing schemes co- ordinated across europe by the european Union for Bird Ringing (euring).
According to Britain’s national bird vote, our favourite bird is the robin, Erithacus rubecula. Its average lifespan is 1.1 years, yet once one reaches adulthood, it can survive for far longer. The record for the oldest ringed robin was 19 years and four months, found in the Czech Republic.
Our second favourite, the barn owl ( Tyto alba), has an average life expectancy of two to three years. Yet in the Netherlands, a wild barn owl lived to 17 years ten months, and in england, a captive female barn owl was retired from breeding at 25.
Number three, the blackbird, Turdus merula, has an average lifespan of 2.4 years. The oldest one found, in Germany, was 21 years and ten months old. Number four, the tiny wren, Troglodytes troglodytes, averages two years. Its longevity is poor — the oldest example being a British bird aged six years and nine months.
At five was the Red Kite, Milvus milvus, once considered a pest and all but wiped out. It lives on average for eight to ten years, reflecting its protected status, the record being a bird aged 25 years and eight months that was shot down in Germany.
Most avian longevity records in wild birds are held by seabirds. This might surprise us as the sea seems a dangerous place, but these birds have adapted well to their habitat, which is free from predation and habitat loss inflicted by man.
Indeed, seabirds are most in danger when they come to land to breed each spring and summer. To avoid predators such as rats and foxes, they nest in colonies on steep cliffs and offshore islands.
The oldest bird ever recorded was a Manx shearwater, Puffinus puffinus, which was described as already an ‘adult’ when it was ringed on Bardsey Island, off the west coast of Wales, in 1957. It was recaptured in the same location 50 years and 11 months later, in 2008. It might still be alive.
This bird had already lasted almost a decade longer than the next longest living on record, a 41-year- old razorbill, Alca torda, monitored in 2004, also on Bardsey Island, and a 40-year-old fulmar, Fulmarus glacialis, at eynhallow, in Orkney, in 1992.
Mrs Beth Colley, Tenby, Pembs. QUESTION When was napalm first used by U.S. forces? The U.S. Army Air Corps acquired its first two incendiary bombs in 1940, both of British design.
The M47 weighed 100lb and was filled with rubber and coconut oil blended with gasoline, and was designed to penetrate the roofs of large buildings. The M50, weighing 4lb, made of magnesium and filled with powdered aluminium and iron oxide, was intended to be dropped in clusters on lighter buildings. Both were used to some extent throughout the war.
In late 1941, partly as a result of a shortage of magnesium, a scientific team at harvard was given the job of producing an alternative to the M50 small bomb.
In due course the gel filler for the bomb, designated M69, became the standard in due course for U.S. incendiaries. The combination of naphthenic and palmitic acids, known as ‘napalm’, was combined with gasoline to produce a thick jelly, that in time also became known as ‘napalm’.
The small 6.2lb bomb designed to hold the filler had a 3ft streamer that stabilised it and controlled its velocity. When it hit a solid surface, a TNT charge would go off, spreading the napalm as far as 100ft (30m) and igniting it. Such bombs were designed to be dropped in clusters.
The M69 was offered to the British who, after t ests, declined i t as having insufficient roof-penetrating power for typical German structures. But by late 1943 the Americans realised the lightly built and densely concentrated residential and industrial areas of Japanese cities such as Tokyo might be ideal targets for these napalm-filled bombs.
Once the Marianas Islands of Saipan, Tinian and Guam were captured in the summer of 1944, the Americans began to build the five massive airfields that would house their B-29 Superfortress bombers.
Raids began in November 1944 with a 100-plane sortie on Tokyo, and gradually more B-29s were moved to the Marianas. There were 1,000 by the end of the war.
early raids using M69 proved satisfactorily destructive, and in March 1945 it was decided systematically to destroy the war-making potential of Japan’s major cities.
This began with the raid on Tokyo on March 9/10 (the Americans having decided that, unlike in europe, low-level night bombing would be the most effective). A total of 338 B-29s from three U.S. wings dropped 2,000 tons of napalm incendiaries on the heart of the city.
About 100,000 people died (twice as many as Britain lost in the whole war through bombing, and more than the original death toll at hiroshima), and 16 square miles of the city were burned out.
After such an overwhelmingly ‘successful’ demonstration of its effectiveness, the future of napalm was assured.
Norman Wallace, Church Stretton, Shropshire. QUESTION When and why was the term ‘Bomber County’ used to describe Lincolnshire? FURTheR to earlier answers, the aircraft before the Lancaster was the Avro Manchester, which was a very good airframe spoilt by two under- developed Rolls-Royce Vulture engines.
The Vulture engine was two V12 RollsRoyce Kestrel engines joined on a common crankshaft and crankcase. The Vulture was being developed at the same time as the Rolls-Royce Merlin, which had greater priority because the Merlin was needed during the Battle of Britain.
The very capable Manchester airframe was subsequently married to four Merlin engines to become the Lancaster.
Fortunately f or Great Britain, the heinkel 177, the Luftwaffe’s only heavy, l ong- r ange bomber, had a s i milar problem. The Germans used two engines and a gearbox to drive one large propeller, but this set-up was even less reliable than the Rolls-Royce Vulture and very prone to engine fires. The he 177 was also designed with four separate engines, but this model was never used in action.
The two engines and gearbox system was l ater successfully used on B36 bombers, using large, air-cooled engines. In the late Forties, Armstrong Siddeley built a good- l ooking Double Mamba twin turboprop engine/gearbox, which was fitted only in the Fairey Gannet bomber used by the Dutch, German and Royal Navies.
M. French, Downham Market, Norfolk.