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page.About Birds in General
Birds are higher vertebrates with a constant and fairly high body temperature ranging from 38 °C to 44 °C. They have two pairs of limbs, the front pair being in the form of wings which are usually used for flying. Some species of birds, however, have frail wings incapable of supporting them in flight, for example in the case of the ostrich, or adapted only for swimming, as in the case of penguins. All the birds depicted in this book are capable of flight.
Birds evolved over millions of years from reptiles, with which they share many common features to this day. For instance, some reptiles and all birds lay eggs and have a comparable arrangement of the reproductive and excretory organs, the ducts of which share a common opening with the gut - the cloaca. The develop-ment of their embryos is also similar.
The first creatures to develop characteristic avian features such as feathered wings appeared about 150 million years ago, in the Jurassic period of the Mesozoic. These primitive birds, about the size of a pigeon, possessed a bill provided with teeth, had three free fingers ter-minating in claws on the fore limbs and a long tail composed of 23 vertebrae with feathers ar-ranged in two rows on either side. These primi-tive birds were called Archaeopteryx. Perfect fossil remains were found in Upper Jurassic slate formations in Bavaria.
These birds were incapable of strong flight, mostly climbing trees and using their wings for `parachuting' or gliding.
The fossil remains of another extinct bird, Hesperornis, were also found in the North American Chalk of western Kansas. This bird was incapable of flight, had finely toothed jaws, and resembled the present-day divers. It lived between 70 and 140 million years ago. Other primitive birds living at this time included Ichthyornis, Apatornis, etc. None of these primitive birds survived the end of the Creta-ceous period which marked the end of the Mesozoic and onset of the Tertiary, which brought with it many genera and species of birds that later likewise became extinct, but also species greatly resembling those of the present day and from which the present species evolved.
Because the taste buds are located quite deep inside the mouth on the soft upper palate and on the mucous membrane underneath the tongue and because birds, unlike mammals, do not chew their food but swallow it quickly they have little sense of taste. In most birds the sense of smell is also very poorly developed and they are not aware of scent at all.
The sense of touch is developed in varying degrees. Birds generally have such sensory or-gans inside the 'bill and on the tongue, but some also have them at the base of certain feathers and on the legs, etc. Birds that obtain their food from the ground even have these organs at the tip of the bill.
A bird's most perfect and important sensory organ is the eye. Birds see far better than other animals. The eye is large and focuses not only by means of muscles squeezing the lens as in the case of mammals, but also by flattening or bulg-ing. The eyes can also be moved independently and thus each can be looking at a different object at one and the same time. The eyes are usually located on either side of the head and thus each has its own field of vision. Some birds, such as owls, however, have both eyes facing forward, but they are able to turn their head a full 180° each way. Colour vision in birds is about the same as in man. In addition to the upper and lower eyelid birds have another special lid called the nictitating membrane which extends from the inner corner and can cover the entire eye. The retina has a greater density of sensory cells than the eye of man, more than five times as many in the case of raptors, thus ena-bling them to see their prey even from a great height.
Another important sensory organ is the ear, even though of less perfect structure and still resembling that of the reptiles. There is only one earbone, corresponding to the stirrup in the human ear, and the external ear channel is com-paratively short. Despite this a bird's hearing is very good and in some species, such as the owls, it is excellent and put to good use in hunting prey at night. The outer ear of birds has no lobe and is usually covered with feathers.
The vocal organs, located at the lower end of the trachea, likewise play an important role in the life of birds. This organ, called the syrinx, is remarkably well developed in songbirds, but less so in other groups of birds which usually have a monotonous call or produce only raucous sounds. Some, such as the white stork, have no vocal organs and communicate by clapping their mandibles together.
The bird skeleton is not only strong but also light, because most of the bones are hollow and filled with air. The long bones, in particular, are tubular and very strong, and their inner pneumatic filling greatly reduces the weight of the whole skeleton - a very important factor in flight. Birds' feathers are also very light and arranged to form an impermeable surface that traps `cushions' of air. The breastbone is re-markably well developed and anchors the pow-erful muscles, which raise and lower the wings.
Click on any of the other bird links, these are Geese
Barnacle Goose : Brent Goose : Canada Goose : Greylag Goose
Or on the Ducks:
Gadwall : Goldeneye : Goosander : Mallard : Pintail : Pochard : Red Breasted Merganser
Red Crested Pochard : Shellduck : Shoveler : Teal : Tufted Duck : Wigeon
And the rest, in no real order of importance:
Common Sandpiper : Coot. : Corncrake : Curlew. : Dunlin : Greenshank : Lapwing : Moorhen : Oystercatcher : Redshank : Ringed Plover : Snipe : Spotted Crake : Stone Curlew : Turnstone : Whimbrel : Woodcock.
Problems Caused by Certain Sea Birds
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