Bill – The mouth parts of the bird, extending from the base (the part connected to the bird's head) to the tip (the part furthest from the bird's head).. A bill’s shape will often say a lot about the diet of the bird. For example, stout, conical bills are used for crushing seeds while long, spearlike bills are well-suited to catching fish.
Breast – A bird's breast is the section of its plumage between the throat and the belly.
Call – A bird’s call is usually a note, pair of notes, or short series that the bird will use regularly. Calls often serve to keep birds aware of each other’s location or to sound an alarm when a predator approaches.
Cap – A bird's cap consists of the feathers on top of its head. Many birds, such as the red-bellied woodpecker and the green heron, have distinctively colored caps that aid in identification.
Crest – A crest is a pointed tuft of feathers rising from the bird’s crown. Many birds (such as the Northern cardinal and the tufted titmouse) can raise and lower their crests at will, but some (such as the great blue heron) cannot.
Epaulets – Epaulets are specially adapted patches of feathers on a bird's shoulders that can be concealed or revealed by sliding another group of feathers over them. Only a few species (such as the red-winged blackbird) have distinctively colored epaulets.
Eye-ring – Some birds have distinctly colored eye-rings. More often white than anything else, the eye-ring is composed of a circle of unfeathered skin immediately surrounding the eye.
Malar stripe - Malar stripes are stripes of color extending from the base of a bird's bill backwards and downwards to the side of its neck.
Mob - A group of birds that band together to harass another bird - usually one they perceive to be an intruder or a threat, or occasionally simply because it has food.
Nape – A bird's nape consists of the feathers on the back of its neck, usually extending from its shoulders to the back of its skull.
Primary feathers – The primary wing feathers of a bird are the long feathers found at the the lower outside edge of the wing. They sometimes resemble fingers, and are generally not visible in a folded wing.
Raptor – Comprised of hawks, falcons, eagles, owls, and vultures, the raptors are a group of birds characterized by their method of hunting and predatory countenance. A raptor usually has powerful feet with sharp talons to grasp prey and a sharp, hooked beak for tearing flesh. Raptors tend to be powerful fliers.
Rump – The rump is a patch of feathers immediately above the base of a bird’s tail. The rump is often covered by the folded wings when the bird is at rest, but rump patches become clearly visible when the bird takes flight.
Secondary feathers – The secondary wing feathers of a bird are the long feathers found at the lower inside edge of the wing. The tips of the secondaries are often visible in a folded wing.
Sexual dimorphism – Many birds are sexually dimorphic, which means that the male and female birds display different plumages. When the plumages are different enough to complicate field identifications, the differences are noted in the species entry.
Song – A song is a musical, often complex series of notes and phrases which may or may not be repeated. Not all birds sing, but those that do can most often be heard in the spring and summer. Songs serve to attract mates and establish territory, though some scientists believe that birds occasionally sing for enjoyment only.
Songbird - Comprised of a great many small birds including thrushes, warblers, finches, and sparrows, the songbirds are a diverse group. A songbird usually perches in trees and generally possesses a melodic voice.
Speculum – Generally seen only in ducks, the speculum is a bright band of iridescent color on the wings. Although they may occasionally be visible, birds often keep their specula concealed when at rest. In flight, however, the speculum is clearly visible as a shining colored band stretching along the lower inside edge of the wing.
Tail – A bird’s tail may be nearly any length and shape, but most bird tails appear rectangular and square-edged when the bird is at rest. In flight, the tail is often spread out like a fan to aid the bird in maneuvering and braking.
Throat – A bird's throat is the section of plumage that extends from the base of the bird's lower mandible to the upper boundaries of its breast. Some birds (such as the white-throated sparrow) have conspicuously colored throat patches that can aid in identification.
Wader – Comprised of herons and a few long-legged sandpipers, the waders are a group of birds characterized by their method of feeding. A wader usually has long legs well-suited to wading into shallow water to catch fish and shellfish.
Wing-bar – Often, a bird will have discernible bars between the “sections” of its folded wing, generally between the greater and median coverts and the median coverts and secondary wing feathers. The presence or absence of these wing-bars is often an important character for small songbirds such as warblers.
Wingspan – A bird’s wingspan is measured from the tip of one wing to the tip of the other.