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Birds are a group of warm blooded (endothermic) vertebrates, characterized by feathers, a beak with no teeth, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton.
Having two legs and two wings puts birds in the class of tetrapods. Birds live worldwide and range in size from the 2 inch (5 cm) bee hummingbird to the 9 foot (2.75 m) ostrich.
The branch of zoology involved in the study of birds is called Ornithology. Those who study birds are called Ornithologist and the current belief of most of these specialist is that birds are the last surviving dinosaurs having come from feathered ancestors within the theropod group of saurischian dinosaurs.
According to the ornithologists, the fossil record shows that true birds first appeared during the early Mesozoic Era, during the
Triassic period over 200 million years ago (mya).
Later, from the end of the Mesozoic Era through the beginning of the Cenozoic Era, during the Cretaceous–Paleogene periods about 66 mya, when extinction events killed off all other dinosaurs, the birds and other animals, specifically those in the southern hemisphere, however, survived these extinction events.
Then, while ocean levels were much lower during periods of global cooling, the birds and other animals migrated across land bridges to other parts of the earth. Often, humans were right on the heals of the animals following the migration of those they had come to enjoy eating.
Some birds, especially corvids (crow family) and parrots, are among the most intelligent animals. Several bird species, including corvids, nuthatches, owls, parrots, seaguls, and warblers make and use tools.
Also, many species annually migrate great distances, making a three thousand mile trip short in comparison to the long distance champion, the arctic tern who travels from the Arctic to the Antarctic, a journey of 14,000 miles (22,000 km) in as little as three months.
Birds are social, communicating with visual signals, calls, and bird songs. Many participate in such social behaviors as cooperative breeding and hunting, flocking, and mobbing of predators.
The vast majority of bird species are socially monogamous, usually for one breeding season at a time, sometimes for years, but rarely for life. Other species have polygynous (many females) or, rarely, a polyandrous (many males) breeding systems.
Birds produce offspring by laying eggs which are fertilized through sexual reproduction. They are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching. Some birds, such as hens, lay eggs even when not fertilized, though unfertilized eggs do not produce offspring.
Orders of the Class Aves
Ornithologist has divided the class of aves into many orders, however, when I began to photograph and study birds for myself, I found that those who do the classifying of birds, have made it to hard to understand by myself as well as others who are interested in these winged fellow creatures.
Biologists and especially Ornithologist have been classifying birds into groups for hundreds of years and still these biologists have not come to a consensus in their classification of animals in evolution and DNA sequencing orders.
Due to their confusing categories of classification, a problem has resulted for all of us who have not been taught in their universities. In order to locate a specific bird on the list of birds, one must know and understand these evolution and DNA sequencing orders, just to find the bird in the guide book.
One thing remains a certainty, the vastness of God′s creation is truly amazing. So, to make it easier for me to locate the birds, I have ordered them into several sub-classes before looking at the orders and families divisions.
The Classifications of this Gallery
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In my examination of the feathered creatures, I have come across a unique way of classifying birds, particularly those on this continent, a classification which involves dividing birds into sub-groups.
The sub-groups are listed alphabetically in this gallery, are five in number and of these groups, the first group are all those birds found only in the Arctic areas, after which there are two groups are land birds, and two groups are water birds.
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