Best birds and DNA testing resource on the web
 

Welcome to our birds ad DNA testing Archive!

 

(Browse for more articles)

 

Biology - Birds, An Introduction

Birds evolved from reptilian ancestors in when sea-birds use the currents of wind
the Jurassic period, 200 million years blowing up a cliff face.
ago. At the same time, mammals were In flapping flight, powerful muscles
evolving from a different line of depress and raise the wing rhythmically,
reptilians. forcing air down and backwards which
The most characteristic feature of birds gives the bird lift and forward movement.
is the possession of feathers. Because During the up-stroke the wings are flexed
the bird-like reptiles of the Jurassic at the wrist and offer less air
were becoming warm-blooded, the principle resistance than in the down-stroke where
advantage of the feathery covering was they are fully extended. The way the
probably the reduction of heat loss from flight feathers overlap also helps; air
a warm body. Modern birds have pressure forces the vanes apart on the
temperatures of about 40-41 degrees C upstroke but closes them on the
which contributes to the high rate of down-stroke.
metabolism necessary for the muscular Apart from the wings, other features help
activity involved in flight. to make flight possible. The contour
The upper and lower mandibles of a bird feathers give the bird a streamlined
are extended to form a beak. The shape of shape; the bones are hollow and therefore
the beak varies with the species. There very light; parts of the skeleton are
are long, narrow beaks which penetrate fused together making a rigid 'box' which
into flowers for their nectar; short resists the tendency to be squashed when
stout beaks which crack open seeds; the flight muscles contract; the flight
sharp, hooked beaks which tear flesh from muscles are very powerful and are
prey. attached to a keel-like extension of the
There are two layers of feathers covering breastbone; the bird's raised temperature
the body. The down feathers are fluffy enhances the high metabolic rate which is
and form an insulating layer close to the needed to supply the energy for flapping
body. The contour feathers are flatter flight.
and broader and make a waterproof layer All birds reproduce by eggs which are
as well as giving the bird its fertilised before laying. The male bird,
characteristic shape The power of flight after a successful courtship display,
became possible as the skeleton of the mounts the female, applies his cloaca to
fore-limbs became modified to form wings hers and passes sperms into her
and the flight feathers developed. The reproductive tract. As the eggs travel
flight feathers on the wings have long down the oviduct, a layer of albumen is
shafts and flat vanes on each side of the added and finally a hard shell. The eggs
shaft. The vanes are formed from are laid in a nest which may be carefully
parallel rows of fine filaments which constructed from vegetation or be simply
interlock in such way that, should the a scrape in the ground or a ledge on a
feathers be damaged, they can easily be cliff. The eggs are kept warm by
restored by preening with the beak. incubation. That is, the bird covers them
The feathers are produced from pits in with her body where they are kept close
the skin, much as hairs are produced in to the skin. The young finally hatch out
mammals. Muscles in the skin can move the by pecking their way out of the shell.
feathers, fluffing them out in cold The chicks of ground-nesting birds,
weather for example. The skin is loose including waterfowl, hatch out with a
and dry with few glands except for an downy covering of feathers and can run
oil-secreting gland which carries the about or swim in a very short time. They
tail feathers. The birds spread the oil stay close to the parent bird who, in the
from this gland over their feathers when case of waterfowl, may feed them or they
they preen, thus increasing the water may simply forage for food, learning what
repellent properties. is suitable or unsuitable to eat.
Flight is of three kinds, soaring, The chicks which hatch in nests above
gliding and flapping. For gliding and ground are often without feathers and are
soaring the bird extends its wings, kept warm by the adult brooding them,
keeping them still except for small that is, covering them with the body,
adjustments. In soaring, the bird is which also keeps off the rain. Both
carried upwards on currents of warm air adults bring food to the nest and feed
(thermals) rising from the ground. In the chicks until they are old enough to
gliding the bird slowly loses height leave the nest, and continue to feed them
while gaining forward momentum. These for some time afterwards.
forms of flying may be combined, e.g.




www.birdsexing.com keyword stats [2008-04-12-2008-04-12]



Daily top traffic source : MSN
Historical MSN keyword trend


Most current MSN search phrases:

SEXING DUCKS


Other search engines trends:



Other search phrases:

DNA Testing "Birds" a picture of a guitar with tweety bird
to kill the moking bird ragnarok pet guide
birds reproduce vertebraes birds and dinosaurs
birds observe
bird names non gender choose
Pets Help Being Lonely beat a paternity test
sexing games Teaching Parrots How To Talk
Chemical Pregnancy Symptom sexing emus
evolution discharge in early pregnancy dog
early pregnancy + discharge love bird skeleton
evolved skeleton birds allergy
I know why the caged birds sings





1- A- 2- 3- 4- 5- 6- 7- 8- 9- 10- 11- 12- 13- 14- 15- 16- 17- 18- 19- 20- 21- 22- 23- 24- 25- 26- 27- 28- 29- 30- 31- 32- 33- 34- 35- 36- 37- 38- 39- 40- 41- 42- 43- 44- 45- 46- 47- 48-