This
fortnightly feature was published on September 13, 1998
The
laughing dove
BESIDES cattle egret the other
Indian bird which invaded other countries of the world in
a big way is the collared turtle dove (also known as
collared dove). Till 1930 this bird was unknown to
Europeans, but now it is a well established species in
the countries of Europe.
A native of India and
western and southern China, collared dove was introduced
to Asia Minor in 16th century where it was kept in
semi-captivity at the courts of various sultans. Later in
the 18th century the species began to spread further
across Asia Minor and at the same time eastward as far as
Japan. During the 20th century the species spread
north-westwards right through Europe from a range once
restricted to Turkey, Albania, Bulgaria and former
Yugoslavia. It spread throughout the entire Balkan
Peninsula and appeared in Bucharest, Budapest, Prague,
Hannover, Munich, and in 1951 even as far north as
Rostock. In 1952 it appeared in England, Norway and
Belgium for the first time, and in 1964 in Iceland. Prior
to this collared dove reached Hungary in 1932, Austria in
1938, Germany in 1943, Netherlands in 1947, Sweden and
Switzerland in 1949 and France in 1950. It is rapidly
becoming established everywhere, multiplying at an
amazing rate and seemingly impervious to long, hard
winters.
To this day no one is able
to explain what prompted the dove to leave its home in
the warm climate of India.
This bird is predominantly
a seed and grain eater. Consequently its close
association with man has brought it in conflict with
humans and now they are being shot in many European
countries as pests.
The word pigeon and dove
are used very loosely. In fact there is no big difference
between the two kinds except for the size. It is the
larger species which are usually called pigeons and the
smaller doves. In both these groups both parents share
the family duties, which also include incubation and
rearing the young. These birds feed their young with
milk, produced not in mammary glands as in
the case of mammals, but by the walls of the crop. This
substance is called crop milk or pigeon
milk which is brought about by prolactin, a
lactogenic hormone (protein hormone secreted by
adenohypophysis or anterior pituitary, that initiates
lactation in mammals and stimulates the production of
progesterone by the corpus luteum). With the secretion of
this hormone the walls of their crops (pouch in
birds gullet) thickens and the crop milk starts
oozing. The milk is produced by both the
parents on which squabs are fed. This creamy cheese-like
substance contains all essential ingredients like
proteins, fats, minerals, and vitamins. To get this
"milk" the young ones thrust their heads into
their parents beak.
Birds living in deserts
employ techniques to keep their body cool. Among these
the strategy which the mourning dove has adopted is a
unique one. It allows its body temperature to rise above
normal to around 45° C (for many species this
temperature can prove fatal), so that their body
temperature goes higher than their surroundings, enabling
further heat to be lost through conduction and radiation,
which causes a cooling effect.
Doves belong to the
Columbidae family which has about 300 species and are
found worldwide. The characteristic quality of these
gregarious birds is that they drink like horses by
immersing their bills in the water and sucking it up,
while most birds have to raise their heads so that the
water can trickle down from the bills.
Some species of doves are
found in Australia, out of which Senegal or laughing
turtledove is not there for very long. Exactly 100 years
ago in the year 1898 some pairs were released from the
South Perth zoo. This species spread widely, but mainly
in urban area. Its pleasing appearance makes it an
attractive bird, and the call, although being the typical
pigeon coo, has an unmistakable laughing quality. Now it
is found over the southwest of Australia.
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