page_title: Glossary of bird terms
section_title: D
hierarchical_section_title: Glossary of bird terms / D
caption_attribution_description: Eider à duvet
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: definitive plumage 
  Adult plumage sufficiently developed and fixed following the juvenile years such that it no longer changes significantly in appearance with age.
  diastataxis
  The state of lacking a fifth secondary feather on each wing, which occurs in birds in more than 40 non-passerine families. In these birds, the fifth set of secondary covert feathers does not cover any remex. Loons, grebes, pelicans, hawks and eagles, cranes, sandpipers, gulls, parrots and owls are among the families missing this feather.
  dietary classification terms (-vores) 
  Birds may be classified by terms related to the types of foods they forage for and eat. The -vore suffix is derived from the Latin vorare, meaning 'to devour'. Equivalent adjectives can be formed through use of the suffix -vorous. For example, granivore (n.) / granivorous (adj.). Generally, classification terms are used based on predominance of food source and/or specialization. There can be much cross-over and mixing between classifications. For example, insectivores and piscivores may at times be described more broadly as types of carnivores, and hummingbirds, though they do eat insects, are often described as nectarivores, rather than insectivores, as nectar is a specialized and predominant food foraging source for that bird family. The feeding strategies of birds is intimately tied to their physiology and evolutionary development. For example, beak shape and structure such as the makeup of the tomia, the presence (or not) of a bill tip organ, and myriad other adaptations are tied to a species' feeding strategies. Feeding habits also correlate with aspects of brain development and size. For example, the spatial memory of birds that store food in various locations has been shown to be highly developed and contributes towards success at that feeding tactic.
  dimorphism
  See sexual dimorphism.
  diving 
  Also defined: surface diving; plunge diving. Some birds dive into the water for food. Two diving strategies are differentiated: surface diving birds dive from the surface of the water and swim actively underwater; and plunge diving birds dive from the air into the water. Plunge diving birds may use the momentum from the plunge to propel themselves underwater, whereas others may swim actively.
  down 
  Also, down feathers or plumulaceous feathers. The down of birds—their plumulaceous feathers, as opposed to pennaceous feathers—are a layer of fine, silky feathers found under the tougher exterior feathers, that are often used by humans as a thermal insulator and padding in goods such as jackets, bedding, pillows and sleeping bags. Considered to be the "simplest" of all feather types, down feathers have a short or vestigial rachis (shaft), few barbs and barbules that lack hooks, and (unlike contour feathers) grow from both the pterylae and the apteria. Very young birds are clad only in down. The loose structure of down feathers traps air, which helps to insulate birds against heat loss and contributes to the buoyancy of waterbirds. Species that experience annual temperature fluctuations typically have more down feathers following their autumn moult. There are three types of down: natal down, body down and powder down.
  drumming
  A form of non-vocal communication engaged in by members of the woodpecker family. It involves the beak striking a hard surface multiple times per second. The drumming pattern, the number of beats per roll and the gap between rolls is specific to each species. Drumming is usually associated with territorial behaviour, with male birds drumming more frequently than females. Drumming may also refer to the sounds produced by the specialised outer tail-feathers of snipe in the course of their courtship display flights.
caption: A female common eider sits on her nest, surrounded by down feathers
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