Critical Thinking

Introduction Its legs and feet are strong in

Introduction

The Dipper (Cinclus Cinclus) is a native British bird found
in most parts of the UK (As shown in figure 1) near fast-flowing rivers in
upland areas and some lowland areas too. These birds are plump and short tailed
in appearance and have a unique low whirring flight path. The Dipper has some adaptations
to help it survive in this rough environment. It has very dense plumage to keep
out the icy water. Its feathers are heavily waterproofed with copious oil from
its quite large preen-gland. Its body is streamlined so that the water flows past
easily stopping friction for these birds to navigate fast. Its legs and feet
are strong in order to grip rocks around the water. The wings, which allow the
bird to swim through the water and currents, have strong muscles to help push
against water resistance. The Dipper also has flaps over its nostrils that
close when the bird has submerged stopping these species from breathing in the
water and finally, its eyes are designed to cope with vision in the medium of
water allowing it to find food efficiently. Dippers, like a lot of river birds,
are highly territorial birds. In their stormy habitat, communication can be a
problem and is thought that this is the explanation as to why Dippers dip. The
Dippers dip by flexing their legs rapidly, like a rapid curtsey, where the
Dippers do it repeatedly especially in territorial encounters; this makes it an
almost certainly a signal showing a bird’s occurrence. Another signal is
blinking. Dippers are unusual in having completely feathered eyelids, which
happen to be white, and when a bird blinks they are highly visible. Blinking
tends to occur with the dipping display, and is also probably a signal. Dippers
moisten their eyes but this is done by the transparent third eyelid, the
so-called nictitating membrane. This is vital in order to clean the eyes from
any foreign objects.

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Habitat

The Dipper is truly the world’s only tune-bird to be aquatic
based on habitual total involvement as a way of life. Taking into account that
these birds have no external adaptations to diving – no webbed feet etc. – it
is expected that these birds take an easy option and be maybe half-aquatic,
swimming around in still, and gentle water. The Dipper lives on rivers with
strong, challenging currents and white water, where even the ducks are hardly
seen. The Dipper acquires most of its prey from the stream bed by turning over
pebbles with its strong beak for finding food that is hidden beneath them. To
do this efficiently it uses its wings to “fly” against the current as well keeping
its wings on the riverbed. It also grips with its feet, holding on to the
ground to help prevent it from being moved by the currents Remarkably, a Dipper
doesn’t fly up and dive into the water, just as a other birds would, using its
momentum to submerge. It can humbly walk into the water. At times, it will
splash in while flying, or jump in from a rock too, and it will float on its
belly, with wings spread just like paddles. It appears to be a master of its
environment. Dippers seem to be almost resistant to the cold. They sometimes
hunt for food under the ice, and can be found in temperatures down to -45°C
particularly in the most highest of altitudes of the Urals, although rivers are
abandoned if they freeze over completely. The birds may move up to 1000 km to
the south, or simply downstream looking for a new habitat for the numbers to
survive.

 

Feeding

These birds are intelligent in finding food underwater. The
Dipper mainly searches for its food under water for its main food source and
targets (aquatic invertebrates including mayfly nymphs and caddis fly
larvae and small fish such as minnows) from the bottom of a
stream/river bed. These birds have evolved a body that is perfect for diving,
swimming and walking on the river bed. Swallowing food is mostly done
underwater but it does bring in larger prey to land, undigested foods are
regurgitated as pellets. Dippers are known to hunt for food along stream bangs
by overturning rock and stones.

Figure 1.

 

Conservation

There is
no conservation projects on/including the Dipper as of now, but reducing
pollution can be beneficial for the species. Additionally this species is
classed as a Least Concern (LC) on the IUCN Red List.

 

Population

The Dipper is in no serious threat of extinction at
this moment in time but local extinctions have been heard of; the population of
the Dipper is relatively stable regionally. From 1970, Dippers have plummeted in west Wales, south-west and north-east England
and in various parts of Scotland but the population in other areas have been
stable. This is due to an increase of pollutants in the air causing acidic
streams of water. This can have a huge impact on offspring as the acid causes
calcium-deficiency in females leading to a reduction of the thickness of
eggshells. Fortunately, this catastrophic problem can be resolved by a simple
solution – coniferous trees. These trap acidic pollutants stopping these from
contaminating the land. Industrial pollution is the reason of the decline of
the Dipper in Europe, while hydroelectric power affects the flow of the water
causing food shortages to where the Dippers live.

 

Breeds

Breeds
native to the UK, called gularis, are found in a relatively patchy distribution
in south-west England. These are also native to Afghanistan, Albania,
Algeria, Andorra, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bhutan,
Bosnia and Herzegovina, Bulgaria, China, Croatia, Czech Republic, Denmark,
Estonia, Finland, France, Georgia, Germany, Greece, Hungary, India, Iran –
Islamic Republic of, Iraq, Ireland, Italy, Kazakhstan, Kyrgyzstan, Latvia,
Lebanon, Liechtenstein, Lithuania, Luxembourg, Macedonia – the former Yugoslav
Republic of, Mongolia, Montenegro, Morocco, Myanmar, Nepal, Netherlands,
Norway, Pakistan, Poland, Portugal, Romania, Russian Federation (Central Asian
Russia, Eastern Asian Russia, European Russia), Serbia, Slovakia, Slovenia,
Spain, Sweden, Switzerland, Tajikistan, Turkey, Turkmenistan, Ukraine and
Uzbekistan. Breeds native to only Ireland
are called hibernicus and are found only on the outskirts of Ireland. These
breeds are found widespread in Europe stretching out to Russia and the Urals
and extending also into North Africa. Related species include: Rufous-throated dipper (Cinclus schulzi),
Orange-billed babbler (Turdoides rufescens), Black-cheeked ant-tanager (Habia
atrimaxillaris), Jerdon’s bushlark (Mirafra affinis), Least flycatcher
(Empidonax minimus), Amaui (Myadestes woahensis), Loveridge’s sunbird
(Nectarinia loveridgei), Pine siskin (Carduelis pinus), Grey wagtail (Motacilla
cinerea), Australian yellow white-eye (Zosterops luteus), Mao (Gymnomyza
samoensis), Streak-capped spinetail (Cranioleuca hellmayri), White-tailed
shrike-tyrant (Agriornis albicauda), Kofiau monarch (Monarcha julianae), La
Selle thrush (Turdus swalesi), Black-faced cuckoo-shrike (Coracina
novaehollandiae), Chestnut-bellied cotinga (Doliornis remseni), Russet-mantled
softtail (Thripophaga berlepschi), Cook Islands reed-warbler (Acrocephalus
kerearako), Swainson’s warbler (Limnothlypis swainsonii ), Reunion starling
(Fregilupus varius), Biak monarch (Monarcha brehmii), Namuli apalis (Apalis
lynesi), Rotuma myzomela (Myzomela chermesina), Whitethroat (Sylvia communis), Yellow
weaver (Ploceus megarhynchus), White-capped tanager (Sericossypha albocristata),
Royal parrotfinch (Erythrura regia), Spinifexbird (Eremiornis carteri) and Whistling
warbler (Catharopeza bishopi).

 

Breeding

Some individuals keep both breeding and winter
territories which in some cases, may be the same. They are defended from about
September onwards and may be owned by a pair, or by individuals of either sex.
Both sexes have the ability to sing. The song is adapted to be heard over the
roaring water, as one might expect as this species lives in a noisy habitat,
and is a strained warble often with scratchy, harsh and sweet notes all mixed
together. Regardless of their territorial bent, Dippers in autumn and may roost
in small groups in traditional locations, such as beneath bridges. Dippers are said to be monogamous where
mating pairs only last for the breeding season. Despite this, there has been a
possibility where these pairs last for years for territory purposes. Courtship
starts in January or February of the year, and there may even be construction
and refurbishment of nests. Even migratory Dippers in the far north of Europe
are back on site by March when
the main breeding period starts. Nesting sites for these birds are usually
preferred in natural crevices in stream-side caves or waterfalls however there
have been occasions where these birds have used man-made structures like
bridges for breeding. Very rarely do these birds reuse their nests in which
they line them for the second time. Nest building is done by both sexes over a
28-day period with the female completing the lining of the nest. Typical Dipper
nests are dome in shape made out of leaves, grass stems and moss as the
infrastructure. The entrance of the nest is wide and points down towards the
water. Female Dippers lay four to five eggs daily (known as a clutch). These
clutches are normally laid between March and May but if a good quality nest is
built in an advantageous environment, sightings of clutches can be spotted as
early as February. Pairs that are in acidic areas lay smaller clutches a little
later and only a few chicks survive therefore making the brood smaller than
normal. These pairs very rarely attempt to make a second brood. These eggs are
incubated for 16 days by the female starting with the last egg so that the eggs
hatch simultaneously to one another. The young are brooded for 12 to 13 days
where they are fed by both parents. The young fledge from the nest from 20 to
24 days after hatching where they are fed for another week. The young then
become independent 11 to 18 days after leaving the nest. The maximum lifespan
of this species is eight years.

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