Sunday, September 13, 1998
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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