MORE THAN 10,000 SPECIES
Class Aves comprises of all the birds in the world. Archaeopteryx is the oldest fossil bird known, dating from the Upper Jurassic period. Little is known about the birds of the Cretaceous period. Major evolution in the bird life took place during the Tertiary period when most of the modern orders appeared.
Birds are not only one of the most beautiful creations of nature, but they are also the only large animals that commonly fly by day. Being most conspicuous to humans they are among the most admired and studied group. The only warm blooded creature that possesses feathers birds have numerous varieties, with 10,240 species – more than twice the number of mammals – and are found on every continent and almost in every habitat.
With constant and fairly high body temperature ranging from 38 degrees C to 44 degrees C, they are higher vertebrates. Their success story begins from the Upper Jurassic period (Jurassic started 19.5 crore or 195 million years ago and lasted approximately 5 crore or 50 million years) when they evolved from the reptilian stock. Both share many common features to this day e.g. all birds and some reptiles lay eggs, development of the embryo is similar and there are many other similarities.
Since birds came into existence, about 20 lakh (2 million) species may have lived at one time or the other, but no more than 12,500 varieties of them probably ever lived at the same time. Of the total number of species alive today a growing number are at risk of dying out because of myriad predators including man and his activities. According to Pierce Brodkorp, a researcher in the University of Florida, since the arrival of Archaeopteryx, over 1,634,000 species have been born and of these only 10,240 survive today.
All bird species are classified into 27 Orders and 155 families. The highest number of them is found in the Neotropical Region – South and Central America, including South Mexico, West Indies and the Galapagos Islands. This region has the richest avifauna in the world and is also known as the ‘bird continent’ with over 2,500 breeding species. As far as the richest bird habitat is concerned, there is no doubt that the tropical forests hold a greater number of birds of a wider variety than any other habitat. Although they occupy merely 7-8 per cent of the total land surface on this planet, they sustain about 45 per cent of all known plants and animals. On the other hand, in sharp contrast to Neotropical Region, the Antarctic region supports the poorest avifauna with only 16 species out of which only 11 breed regularly within the Antarctic Circle.
According to the findings of a global event — Great Backyard Bird Count — held in February 2014, India is home to the largest number of bird species in the world. Participants from 127 countries this time found 4,296 species with India reporting the highest number of 819 followed by Mexico (683), USA (644), Costa Rica (609), Australia (501), Colombia (397), Panama (278) and Peru (138).
A US newspaper, The Kansas City Star, in its report, ‘Want to see a wide variety of birds? Head to India’, said, “India’s emergence as a bird-watching hot spot underscores the rising worldwide popularity of the pastime.” The GBBC was jointly organized by the Cornell Lab of Ornithology, the National Audubon Society and the Bird Studies Canada. Though the US and Canada have been participating in the event since 1998, the first ever such ‘global’ bird count was organized during February 15-18 in 2013 when participants from 110 countries sent their entries.
In 2013 bird watchers from all seven continents had reported and documented 4,258 species from about 180 bird families. Mexico had topped the GBBC list with 645 species followed by the US (638), India (544), Costa Rica (508), Colombia (424), Australia (383), Panama (371) and Peru (325).
The event was launched in 1998 as the first online citizen-science project to collect data on wild birds and to display results in near real-time. Participants during the event period send snapshots of birds as their entries which are subsequently analyzed and documented by the organizers before displaying final results of the GBBC.
India is quite rich in avifauna. It has 16 per cent of the total number of species found in the world, whereas it has only 4 per cent of the land surface. Out of all the species surviving today India has as many as 1200. If we include the subspecies the number goes up to 2061. Of these 1750 are residents and the rest are migratory. Out of the total number of orders and families India has representatives from 20 orders and 77 families.
Among the endemic species of the country – found nowhere else in the world – chir pheasant, found in the West Himalayan conifer and deciduous forests, and the pink-headed duck are the notable examples. Indian bird stock has strong affinity with that of Africa as well as with the birds of Indo-China and very few species are related to the Palaearctic regions.
Of the total avian stock available today globally, some 600 living species are adapted for life on or in water and out of these there are about 265 species that have taken to life at sea. There are 46 living species, subspecies and races of ratites or flightless birds, which include kiwis, ostriches, emus and rheas etc. It has been suggested that they evolved by becoming adult while retaining juvenile features, a process called neoteny. Most of these birds are much larger than flying birds.
All birds have their basics alike; they all have beaks, feathers, wings, two legs, and tails. Despite these similarities, all species differ from one another in one-way or the other. Living in different habitat and leading a different life, these avian creatures have evolved changes in their body machine to suit their environment and life-style.