The boom of the bittern is being heard across Britain once again, after more than a cenh1ry in which the bird has hovered on the edge of extinction.
Noted for its foghorn-like call or "boom", the bittern has made a recovery in numbers that the Royal Society for the Protection of Birds (RSPB) described last year as "a phenomenal success"
However, experts warn that the bird, one of Britain's rarest, still faces severe threats posed by climate change. "Bitterns are not out of danger yet," said Grahame Madge of the RSPB. "On the other hand, this is a very encouraging trend."
Bitterns are a member of the heron family and have the long legs, long neck, dagger-like beak and broad rounded wings. They are smaller than a grey heron at 70 - 80 cms long. Their plumage is a mixture of browns and buffs with lots of dark brown and black streaks and bars giving it a mottled appearance. In flight the rounded wings curve downwards giving them an almost owl-like appearance. Depending on the light they ca11 appear warm orange-brown to dark brown or even black.
The bittern is a secretive bird and its subtle colouring makes it hard to spot in its wetland surroundings—although its mating call testifies to its presence. As yet, scientists do yet fully understand how the male bittern makes its deep "booming" call. It is thought that the bird gulps in air, before expelling it again to produce its loud "boom," which can be heard up to 4.5km (2.8 miles) away. Males are thought to "boom" to alert female bitterns to their presence. Usually the birds "boom" in the twilight at dusk, hidden among the darkness and reeds. Even seeing a bittern in daylight is rare, let alone seeing one produce its mating call.
It was once common across the UK, but numbers began to fall in the Middle Ages—the bird was considered a delicacy and was eaten at banquets up to Tudor times. In the 18th and 19th centuries, the bird became a popular target for taxidermists. The drainage of England's wetlands devastated the surviving population and by 1886 the bird had disappeared from Britain.
Early in the 20th cenh1ry the population slowly began to return and by the 1950s there were 60 bitterns in the UK, but water pollution then destroyed its habitat. By 1997, the bird's numbers had fallen back to 11.
"We created a research programme to save the bittern and discovered the major threat was not the loss of their habitat, but a degradation of it," said Madge. "Bitterns prefer living in particularly wet reed beds, where they can fish easily. But mud often builds up and the reed beds dry up. In large wetlands, sn1all patches will always dry up and new ones form. However, nature reserves are hemmed in today and there is little opportunity for new reed beds to form when the old ones die out." Litter only n1akes the problem worse, he added.
The bittern has been classified by the EU as a "priority species". With European funding, the RSPB lowered reed beds at several reserves and pumped out mud, creating improved habitats. A new site was set up at Lakenheath in Suffolk. Today there are at least 100 bitterns, most of them in southern England.
However, climate change means some habitats are vulnerable to rising sea levels, particularly the important RSPB site at Minsmere in Suffolk, where tides could flood freshwater areas with salt water, ruining them for the bittern. Droughts also endanger the species by drying out wetlands.
The RSPB is now working to create new inland nesting areas. ·"We no longer have a landscape where natural processes can take place on a large scale, so conservationists must work within the areas that are available," said Madge.
"Creating bigger wetlands not only houses a larger diversity of species but also buffers against climate change. If the RSPB's legacy of habitat creation and preservation is maintained, the unique and dynamic bittern's boom can continue to sound out across our wetlands."
Conservationists are particularly excited that Kingfisher's Bridge—a privately-owned newlycreated site in Cambridgeshire—has been the centre for recolonisation of the Fens. The 150-acre wetland site—which in 1995 was Grade 1 arable land—has been partially converted to reed bed by the landowner Andrew Green, with help fron1 wildlife consultant Roger Beecroft.
Andrew Green, the landowner, said: "After all our hard work, we are delighted that bitterns are nesting again in the Fens. We think the key to the project's success is dependent upon a number of factors: good evidence-based habitat management; pure water and control of water levels; the creation of a rich fishery, providing excellent feeding opportunities for bitterns; and the rigorous control of foxes and mink. We are grateful to the RSPB for its research into bitterns, which has helped design an ideal site, and for the supply of reed seeds."
Dr Mark Avery added: "If we thought about it, the RSPB might just be a little envious that Andrew Green has been the first landowner since 1938 to have nesting bitterns in the Fens. We congratulate Andrew on his fantastic achievement and look forward to the spread of this fantastic bird to its rightful home in the heart of East Anglia and, hopefully, to our fenland recreation sites too!"
Choose the appropriate letters A-D and write them in boxes 1-5 on your answer sheet.
1 Experts believe that the bittern
A is still on the edge of dying out.
B is a successful species.
C can fight climate change.
D is disappearing.
2 It is difficult to find a bittern in its habitat because
A it is smaller than a grey heron.
B it hides among the darkness.
C its appearance is colourful.
D it is adept at camouflage.
3 The bittern produces loud booming call to
A alert its natural enemy.
B attract the female.
C gulp in air.
D communicate with other birds.
4 In the Middle Ages the number declined because
A bitterns vanished from Britain.
B bitterns were eaten by eagles.
C bitterns became a target of hunters.
D bitterns became a popular food.
5 Grahame Madge of the RSPB said the main threat to bitterns is that
A nature reserves are few.
B they had no where to live.
C their habitat deteriorates.
D waste pollutes their habitat.
6 Climate change poses a danger to bitterns because
A sea water could flood wetlands.
B they prefer the colder weather.
C reed beds become lower.
D their breeding season is changed.
Choose FOUR letters, A-H.
According to Andrew Green, what are the essential factors when protecting bitterns?
A Control of other birds
B Amply food provision
C Providing reed seeds
D Limiting predators
E Encouraging breeding
F Protecting freshwater
G Well-managed habitat
H Increasing sea level