page_title: Glossary of bird terms
section_title: N
hierarchical_section_title: Glossary of bird terms / N
caption_attribution_description: English: Cropped version of a Lesser Whistling Duck (Dendrocygna javanica) swimming in Singapore.
context_page_description: The following is a glossary of common English language terms used in the description of birds—warm-blooded vertebrates of the class Aves, characterized by feathers, the ability to fly in all but the approximately 60 extant species of flightless birds, toothless, beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart and a strong yet lightweight skeleton.
  Among other details such as size, proportions and shape, terms defining bird features developed and are used to describe features unique to the class—especially evolutionary adaptations that developed to aid flight. There are, for example, numerous terms describing the complex structural makeup of feathers; types of feathers; and their growth and loss.
  There are thousands of terms that are unique to the study of birds. This glossary makes no attempt to cover them all, concentrating on terms that might be found across descriptions of multiple bird species by bird enthusiasts and ornithologists. Though words that are not unique to birds are also covered, such as "back" or "belly", they are defined in relation to other unique features of external bird anatomy, sometimes called "topography".
context_section_description: nail 
  A plate of hard horny tissue at the tip of the beak of all birds in the family Anatidae (ducks, geese and swans). This shield-shaped structure, which sometimes spans the entire width of the beak, is often bent at the tip to form a hook. It serves different purposes depending on the bird's primary food source. Most species use their nails to dig seeds out of mud or vegetation, while diving ducks use theirs to pry molluscs from rocks. There is evidence that the nail may help a bird to grasp things; species which use strong grasping motions to secure their food (such as when catching and holding onto a large squirming frog) have very wide nails. Certain types of mechanoreceptors, nerve cells that are sensitive to pressure, vibration or touch, are located under the nail.
  nares 
  The two holes—circular, oval or slit-like in shape—which lead to the nasal cavities within the bird's skull, and thus to the rest of the respiratory system. In most bird species, the nares are located in the basal third of the upper mandible. Kiwis are a notable exception; their nares are located at the tip of their bills. A handful of species have no external nares. Cormorants and darters have primitive external nares as nestlings, but these close soon after the birds fledge; adults of these species (and gannets and boobies of all ages, which also lack external nostrils) breathe through their mouths. There is typically a septum made of bone or cartilage that separates the two nares, but in some families (including gulls, cranes and New World vultures), the septum is missing. While the nares are uncovered in most species, they are covered with feathers in a few groups of birds, including grouse and ptarmigans, crows and some woodpeckers.
  nasal canthus 
  The area where the eyelids come together at the anterior corner of the eye, on the side of the nares, as opposed to the temporal canthus.
  natal down 
  Also, neossoptiles. Also defined: protoptiles; mesoptiles. The layer of down feathers that cover most birds at some point in their early development. Precocial nestlings are already covered with a layer of down when they hatch, while altricial nestlings develop their down layer within days or weeks of hatching. Megapode hatchlings are the sole exception; they are already covered with contour feathers when they hatch. The natal down coat is usually lost within a week or two of hatching. There are two different kinds of natal down feathers; protoptiles and mesoptiles. The former appears first and the latter appears second. Hathchlings born naked or with a diffuse coat of scant natal down feathers are called psilopaedic, while those born covered with a dense fuzz of natal down are termed ptilopaedic. Compare: body down and powder down.
  nest 
  Also, bird nest. Specialized types: burrow; cavity; cup (adherent  cup; statant cup); dome; dormitory; eyries (or aeries); hanging; ledge; mound; pendant; platform; roost (or winter-nest); scrape; saucer or plate; and sphere. The spot in which a bird lays and incubates its eggs and raises its young. Although the term popularly refers to a specific structure made by the bird itself—such as the grassy cup nest of the American robin or Eurasian blackbird, or the elaborately woven hanging nest of the Montezuma oropendola or the village weaver—for some species, a nest is simply a shallow depression made in sand; for others, it is the knot-hole left by a broken branch, a burrow dug into the ground, a chamber drilled into a tree, an enormous rotting pile of vegetation and earth, a shelf made of dried saliva or a mud dome with an entrance tunnel. The smallest bird nests are those of some hummingbirds, tiny cups which can be a mere 2 cm (0.79 in) across and 2–3 cm (0.79–1.18 in) high. At the other extreme, some nest mounds built by the dusky scrubfowl measure more than 11 m (36 ft) in diameter and stand nearly 5 m (16 ft) tall. Not all bird species build nests. Some species lay their eggs directly on the ground or rocky ledges, while brood parasites lay theirs in the nests of other birds, letting unwitting "foster parents" d
caption: Close up of a lesser whistling duck. Note the hooked nail at the tip of the beak.
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