CONSERVING THE BRITISH BITTERNS
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A
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Breeding
bitterns became extinct in the UK by 1886 but, following re-colonisation
early last century, numbers rose to a peak of about 70 booming (singing)
males in the 1950s, falling to fewer than 20 by the 1990s. In the late
1980s it was clear that the bittern was in trouble, but there was little
information on which to base recovery actions.
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B
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Bitterns have cryptic plumage
and a shy nature, usually remaining hidden within the cover of reedbed
vegetation. Our first challenge was to develop standard methods to monitor
their numbers. The boom of the male bittern is its most distinctive feature
during the breeding season, and we developed a method to count them using
the sound patterns unique to each individual. This not only allows us to be
much more certain of the number of booming males in the UK, but also
enables us to estimate local survival of males from one year to the next
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C
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Our first
direct understanding of the habitat needs of breeding bitterns came from
comparisons of reed bed sites that had lost their booming birds with those
that retained them. This research showed that bitterns had been retained in
reedbeds where the natural process of succession, or drying out, had been
slowed through management. Based on this work, broad recommendations on how
to manage and rehabilitate reedbeds for bitterns were made, and funding was
provided through the EU LIFE Fund to manage 13 sites within the core
breeding range. This project, though led by the RSPB, involved many other
organisations.
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D
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To refine these
recommendations and provide fine-scale, quantitative habitat prescriptions
on the bitterns7 preferred feeding habitat, we radio-tracked male bitterns
on the RSPB’s Minsmere and Leighton Moss reserves. This showed clear
preferences for feeding in the wetter reedbed margins, particularly within
the reedbed next to larger open pools. The average home range sizes of the
male bitterns we followed (about 20 hectares) provided a good indication of
the area of reedbed needed when managing or creating habitat for this
species. Female bitterns undertake all the incubation and care of the
young, so it was important to understand their needs as well. Over the
course of our research, we located 87 bittern nests and found that female
bitterns preferred to nest in areas of continuous vegetation, well into the
reedbed, but where water was still present during the driest part of the
breeding season.
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E
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The success
of the habitat prescriptions developed from this research has been
spectacular. For instance, at Minsmere, booming bittern numbers gradually
increased from one to 10 following reedbed lowering, a management technique
designed to halt the drying out process. After a low point of 11 booming
males in 1997, bittern numbers in Britain responded to all the habitat
management work and started to increase for the first time since the 1950s.
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F
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The final phase of research
involved understanding the diet, survival and dispersal of bittern chicks.
To do this we fitted small radio tags to young bittern chicks in the nest,
to determine their fate through to fledgingand beyond. Many chicks did not
survive to fledging and starvation was found to be the most likely reason
for their demise. The fish prey fed to chicks was dominated by those
species penetrating into the reed edge. So, an important element of recent
studies (including a PhD with the University of Hull) has been the
development of recommendations on habitat and water conditions to promote
healthy native fish populations
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G
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Once independent,
radio-tagged young bitterns were found to seek out new sites during their
first winter; a proportion of these would remain on new sites to breed if
the conditions were suitable. A second EU LIFE funded project aims to
provide these suitable sites in new areas. A network of 19 sites developed
through this partnership project will secure a more sustainable UK bittern
population with successful breeding outside of the core area, less
vulnerable to chance events and sea level rise.
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H
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By 2004, the number of booming
male bitterns in the UK had increased to 55, with almost all of the
increase being on those sites undertaking management based on advice
derived from our research. Although science has been at the core of the
bittern story, success has only been achieved through the trust, hard work
and dedication of all the managers, owners and wardens of sites that have
implemented, in some cases very drastic, management to secure the future of
this wetland species in the UK. The constructed bunds and five major
sluices now control the water level over 82 ha, with a further 50 ha coming
under control in the winter of 2005/06. Reed establishment has principally
used natural regeneration or planted seedlings to provide small core areas
that will in time expand to create a bigger reed area. To date nearly
275,000 seedlings have been planted and reed cover is extensive. Over 3 km
of new ditches have been formed, 3.7 km of existing ditch have been
re-profiled and 2.2 km of old meander (former estuarine features) has been
cleaned out.
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I
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Bitterns now
regularly winter on the site some indication that they are staying longer
into the spring. No breeding has yet occurred but a booming male was
present in the spring of 2004. A range of wildfowl breed, as well as a good
number of reedbed passerines including reed bunting, reed, sedge and
grasshopper warblers. Numbers of wintering shoveler have increased so that
the site now holds a UK important wintering population. Malltraeth Reserve
now forms part of the UK network of key sites for water vole (a UK priority
species) and 12 monitoring transects has been established. Otter and
brown-hare occur on the site as does the rare plant. Pillwort.
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Questions 27-33
The reading passage has seven
paragraphs, A-H
Choose the correct heading for
paragraphs A-H from the list below. Write the correct number, i-viii, in
boxes 14-20 on your answer sheet.
List of Headings
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I.
Research findings into habitats and decisions made
II.
Fluctuation in bittern number
III.
Protect the young bittern
IV.
International cooperation works
V.
Began in calculation of the number
VI.
Importance of food
VII.
Research has been successful.
VIII.
Research into the reedbed
IX.
Reserve established holding bittern in winter
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27
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Paragraph A
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28
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Paragraph B
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29
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Paragraph C
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30
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Paragraph D
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31
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Paragraph F
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32
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Paragraph G
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33
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Paragraph H
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Example:
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Paragraph
E
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Questions 34-39
Answer the questions below.
Choose NO MORE THAN THREE WORDS AND/OR
A NUMBER from the passage for each answer.
34
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When did the bird of bitten reach its peak of number?
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35
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What does the author describe the bittern’s character?
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36
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What is
the main cause for the chick bittern’s death?
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37
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What is the main food for chick bittern?
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38
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What
system does it secure the stability for bittern’s population?
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39
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Besides bittern and rare vegetation, what mammal does the plan
benefit?
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Questions 40
Choose the correct letter, A, B, C or
D.
Write your answers in boxes 40 on your
answer sheet.
40
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What is the main purpose of this passage?
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A
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Main
characteristic of a bird called bittern.
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B
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Cooperation can protect an
endangered species.
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C
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The
difficulty of access information of bittern’s habitat and diet.
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D
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To save wetland and reedbed in
UK.
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