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The beak, bill, or rostrum is an external anatomical structure of birds which is used for eating and for preening, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young. Although beaks vary significantly in size, shape and color, they share a similar underlying structure.
The jaw muscles, which allow the bird to close its beak, attach to the proximal end of the lower mandible and to the bird's skull. [ 5 ] (p148) The muscles that depress the lower mandible are usually weak, except in a few birds such as the starlings and the extinct huia , which have well-developed digastric muscles that aid in foraging by ...
When preening, a bird (such as this red lory) draws individual feathers through its beak, realigning and re-interlocking the barbules.. Preening is a maintenance behaviour found in birds that involves the use of the beak to position feathers, interlock feather barbules that have become separated, clean plumage, and keep ectoparasites in check.
Feeding adaptations in beaks. Birds' diets are varied and often include nectar, fruit, plants, seeds, carrion, and various small animals, including other birds. [78] The digestive system of birds is unique, with a crop for storage and a gizzard that contains swallowed stones for grinding food to compensate for the lack of teeth. [147]
The beak of the sub-group Certhidea, is shown in Fig. 4. The beak of Cactornis is somewhat like that of a starling, and that of the fourth subgroup, Camarhynchus, is slightly parrot-shaped. Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of ...
Herons, by evolutionary adaptation, have long beaks. The classification of the individual heron/egret species is fraught with difficulty, and no clear consensus exists about the correct placement of many species into either of the two major genera, Ardea and Egretta. Similarly, the relationships of the genera in the family are not completely ...
The colour of a bird's beak results from concentrations of pigments—primarily melanins and carotenoids—in the epidermal layers, including the rhamphotheca. [39] In general, beak colour depends on a combination of the bird's hormonal state and diet. Colours are typically brightest as the breeding season approaches and palest after breeding. [40]
Darwin's finches with different sized beaks that were suited for different seed types. Another example of directional selection is the beak size in a specific population of finches. Darwin first observed this in the publication of his book, On the Origin of Species, and he details how the size of the finches beak differs based on environmental ...