This lifeform is found in the SW USA (Texas, New Mexico, and Arizona). This lifeform is found widely in the New World tropics.

Yellow-Green Vireo (Vireo flavoviridis) is a Mexican species that rarely occurs in the lower Rio Grande area. The somewhat yellow color helps identify this species.

Vireos (Vireonidae Family) are a New World group of highly evolved Perching Birds. Although the lines of differentiation between this family and the closely related ones such as the Wood Warblers are not clear, many researchers place 42 species in this family. The following 12 species are known to occur in the United States (an * indicates the species is pictured):

Vireo antiloquus*      Black Whiskered Vireo   Caribbean
Vireo atricapilla      Black Capped            Texas & Mexico
Vireo bellii*          Bell's Vireo            Central & West
                                                United States
Vireo flavifrons*      Yellow Throated         North America
Vireo flavoviridis*    Yellow-Green            Mexico
Vireo gilvus*          Warbling                North America
Vireo griseus          White Eyed              Central and east
                                                United States
Vireo huttoni          Huttons Vireo           Pacific States
Vireo olivaceus*       Red Eyed Vireo          North America
Vireo philadelphius    Philadelphia Vireo      North America
Vireo solitarius*      Blue Headed             North America
Vireo vicinior         Gray Vireo              Southwest United
                                                States and Mexico

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.