Birds are not because they share a few physical characteristics but not nearly enough to belong to the same group. Linnaeus originally defined the class for birds, Aves, in 1758.
More specifically, according to Linnaeus, birds are animals that have feathers, toothless, beaked jaws, four-chambered hearts, lightweight skeletons, and lay eggs with hard, thin shells.
Reptiles, in this system, are any animals that have scaly skin and are ectothermic.
And because reptiles have unique qualities that birds do not share, they belong to the distinct Reptilia class.
Birds are technically speaking reptiles although they are not really classified as reptiles.
According to the phylogenetic classification system, a reptile is any animal which originated from the original group of reptiles, technically including birds and mammals.
Therefore, birds are considered reptiles under Phylogenetic taxonomy, just as other animals that descended from vertebrates are called vertebrates.
Birds are Chordates.
Birds are in the phylum of Chordata or Chordate.
A chordate is an animal of the phylum Chordata.
All chordates possess five synapomorphies, or primary characteristics, at some point during their larval or adulthood stages that distinguish them from all other taxa.
Birds are in the Phylum Chordata (Animals with a backbone).
Next in classification is the Class.
The Class for birds is Aves.
Birds are part of the phylum Chordata, because they meet all the criteria in order to considered part of this phylum.
Birds are a group of warm-blooded vertebrates constituting the class Aves, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton.
Birds reproduce by internal fertilization, during which the egg is fertilized inside the female.
Like reptiles, birds have cloaca, or a single exit and entrance for sperm, eggs, and waste.
The male brings his sperm to the female cloaca.
The sperm fertilizes the egg.
Some of the most basic birds include.
Mourning Doves.
White-Throated Sparrows.
Black-Capped Chickadees.
Pine Grosbeaks.
House Finches.
Mockingbirds.
Bluejays.
Downy Woodpeckers.