Carol Lakanen, age 11, ofOttawa, Ont., Canada, for her question:
HOW MANY DIFFERENT BIRDS ARE THERE?
Almost 9,000 different bird species have been named and classified. Their ancestors arrived during the days of the dinosaurs many millions of years before the human family came to live on the planet earth. Most of them are pretty creatures and some are downright dazzling. They are at home almost everywhere and goodness knows what the modern world would do without them.
Experts tell us that the ancestors of our feathery birds were a branch of the dinosaur clan that took to the air long ages ago. These early birds were whoppers, far bigger than any of our birds. After millions of years, the survivors were smaller and they branched out into various types or species. The Age of Mammals began about 60 million years ago, when the dinosaurs departed. This was a fine time for the birds, also. It seems that all our modern bird species were established about 30 million years ago.
The birds had their greatest heyday during the Pliocene Period, which began 13 million years ago and lasted until the recent ice ages. Bird fossils are hard to find because their delicate bodies soon break apart. However, there are enough fossil records to show that many more species existed during the pleasant Pliocene Period.
It has been estimated that at that time at least 11,600 bird species were at home on the earth. This is almost one third more than our list of modern species. The next period of geological history brought four cruel ice ages and several long spells of mild global weather. Apparently the changing climate was very hard on the birds and hundreds of species were wiped out.
Some scientists classify 8,600 species of modern birds. Others, using slightly different systems, say that the list should be closer to 9,000. In any case, all systems classify the total number in groups of perching birds, land birds, flightless birds, tropical birds and birds of prey.
The birds of a species can mate with each other, but not with another species. However, birds tend to be snappy dressers and some types go in for variations. Our eastern flicker has yellow wing linings and those of the western flicker are red. These two showoffs are classed as subspecies of the flicker species. They qualify as the same bird type with color variations.