This lifeform is found widely in Eurasia. This lifeform is widespread in North America.

Winter Wren (United States) or Common Wren (Europe) (Troglodytes troglodytes) is found in both the New and Old World (older references sometimes call the New World form Nannus hiemalis).

Although it migrates south, it generally breeds in the New World in Canada or the north woods of the United States. Its size, three and a half inches to four and a quarter inches, helps separate this wren from the House Wren which is somewhat larger. Both T. aedon and T. troglodytes have short tails.

There are numerous subspecies in this complex in both the New and Old World.

Wrens (Family Troglodytidae) are a group of 59 New World species that range from northern Canada south to Chile and Argentina. The Common Wren, however, is also found in the Old World. It has been established there for quite some time in that there are almost 30 different geographical races.

Perching Birds (Order Passeriformes) comprise about sixty percent of the world's known species of birds. These 5,000 or so species are broken into many families without very clear distinctions between them. A common characteristic of this order is three forward toes and one reverse pointing toe. Most of species are also characterized by a tendon locking mechanism that permits their feet to lock onto branches when they relax. The families have arbitrarily been placed in alphabetical order.

Aves contains about 8,650 different species of living birds known to science. Each year about one new species is discovered in some remote rain forest or remote island. In addition, scientists have been raising many subspecies to full species status which may raise the species count to 10,000.

However, each year about one species goes extinct. The rate of extinction is increasing, and the rate of new discovery is decreasing, so that the number of bird species will soon begin to decline rapidly. Although different taxonomists would organize the birds differently, there are approximately twenty-seven orders of birds. These orders are broken down into about one hundred and fifty-five different families.

Recent research of the genetic structure of some of the shore birds and owls would indicate that the present organization of orders and families should have some modification.

The birds are a worldwide group of animals that are characterized by having the front limbs modified into wings that are used for flying. Perhaps the most unique feature of the birds is the feathers. These feathers are made up of a central support called a quill and a series of small filaments that are hooked together as barbs.

For many years it was believed that Archaeopteryx discovered in Bavaria was the oldest bird from about 150 million years ago.  However, in l986, Sankar Chattterjee, a Texas paleontologist, reportedly discovered a bird in the genus Protoavis that lived about 225 million years ago.

Backboned Animals (Phylum Chordata) are the most advanced group of animals on earth. These animals are characterized by having a spinal cord or backbone. Most members have a clearly defined brain that controls the organism through a spinal cord. Fish, amphibians, reptiles, birds, and mammals are in this phylum.

Currently, some taxonomists believe that the fish should be divided into two groups (sharks and regular fishes) and that there are some other primitive groups in the phylum such as hagfish or lampreys.

Animal Kingdom contains numerous organisms that feed on other animals or plants. Included in the animal kingdom are the lower marine invertebrates such as sponges and corals, the jointed legged animals such as insects and spiders, and the backboned animals such as fish, amphibians, reptiles, birds, and mammals.