Parakeet is the common name for a small perching pet bird. Although the term is applied generally to any of a number of small parrots with long flat tails, it is more commonly a reference to a specific species with the scientific name (Melopsittacus undulatus) also known as the "budgerigar" or "budgie".
There are two main types of parakeets: the English parakeet and the Australian parakeet. The Australian variety are seen more often in America because the English parakeet has a bigger head, with more feathers surrounding its beak. Wild budgies are known for living near water or in the woods, and come in over one hundred different kinds of color combinations.
Parakeets (or budgies) have many different parts that make up their external features.
Beak: Budgie's beaks are made up of two parts. They have the upper mandible and the lower mandible. Opposite of humans, these birds can move their upper mandible while humans can only move their lower jaw. A substance called keratin covers the bone that makes up the beak. Keratin is made up of tiny blood vessels.
Cere: The nostrils are located right above the beak, and are covered by a tough outer skin called "cere". Males usually have a blue cere, and females usually have a brown cere.
Cheek patch: Below the eye, there is a small patch of different colored feathers. These are usually purple, silver, or grey.
Ear coverts: The ear coverts is the patch of feathers that covers the budgie's external ears.
Eye: These birds have a pupil and an iris. The iris is the area that surrounds the small, black pupil.
Feet: Two of their toes point forwards, and two of their toes point backwards. Therefore, budgies have four toes on one foot, eight all together.
Mantle: The mantle is the patch of feathers that are located above the wings.
Mask: This is the area that has a line that stops right at the bottom of the throat spots. The reason they call this the "mask" is because this area is usually a different color than the rest of the body, and makes the head look like it has a "mask" on.
Rump: This area is located right above the tail, and has an oil gland in it. The bird uses the oil gland to preen itself and other birds. The budgie will take its head and rub it in that gland, and therefore, this gland produces a waterproof chemical.
Tail coverts: There are shorter feathers on the bird's tail that are located underneath the larger tail feathers.
Throat spots: These spots are small and round, and are located right above the mask line. Most budgerigars have 6 throat spots.
Vent: This area is underneath the bird, and can also be called the "cloaca". This is not only used for waste, but is used for reproduction too. Eggs will exit the female in this area. 
For parakeet to reproduce, the male's and the female's cloacas must make contact. Budgie females must go to a hollowed out tree, or if they are pets, they prefer a nesting box. There, they will lay their eggs. When the eggs are laid, they may or may not be fertilized. The female will usually lay about four to twelve eggs. The female budgie will only leave it's nest to stretch. The male budgie almost always comes to the entrance of the nest and feeds the babies.
These birds take about eighteen to twenty days to hatch. At ten days old, they will begin to open their eyes. The mother is only concerned at this point with keeping her babies well fed. After about three weeks, the birds will start developing their adult wings. The male budgerigar will offer to help the female feed and take care of the babies, but the mother doesn't always accept his offer and may take care of the babies by herself. After the fourth week, the birds can live on their own.
By the fifth week of their lives, they can fully live on their own and they begin learning how to fly. The oldest, or the only one in some cases, will start growing away from their parents, and begin to do things on their own. 
Most budgerigars can be found in Australia, by the mainland areas. Rarely will you find a flock on the east coast or the south-west. When budgerigar birds travel, they mostly travel in large, easy-to-see flocks.  You can also find them in open woodland or grassland areas. The flocks do form are usually small, but they can also be a very big size. They fly from place to place depending on how much food or water there is in the area they are in. If there isn't enough, they will fly to a different place. They usually will eat spinifex, wheat, and grass. 
Budgerigars do have a certain breeding schedule that they follow. In the south, they will mate between the months of August and January. In the north, breeding will happen between the months of June and September. 
Budgies also have the ability to sing and mimicry. The males usually pick up the singing and mimicry technique faster than the females. 
What budgerigars can eat:
-white, yellow, and red millet  (A millet is a nutrient filled grain that has many vitamins in it) 
Budgies eat a variety of different fruits and vegetables; those that are listed are just a few examples of what can be fed to budgies. Budgies need to keep eating in order to fly. Flying takes so much energy, that they need to keep bringing in nutrients constantly to keep a healthy energy level. Food actually passes through their digestive tracts in about 3-4 hours. If a budgie is not fed in 48 hours, it could die of starvation. 
Budgies must not eat any of the following, or they can die from poisoning if there is an overdose:
-Milk (and other milk products containing lactose)
Parakeet have an amazing ability that many may not know. They can talk! One budgie-parakeet, holds the record for saying the most words a bird could ever say. Budgies may be hard to understand because of their small size, but if you listen you will be able to hear them talking, or at least trying to talk. It's good to teach a budgie how to talk with only one person and sometime early in the morning. Late at night the birds get more rambunctious, so it's good to avoid those times. It is best to teach them something easy at first, and teach them over and over for about 20-30 minutes. It's suggested to teach them to say "hello, [parakeet's name]". It's also easier to teach smaller, younger birds because they will catch on quicker.
- Budgie Anatomy-Know Your Parts! unknown author, July 20th, 2008.
- About Budgies budgiecare.org, 2008.
- Budgerigar Australian Museum, 2003.
- Small Parrots in Health and Disease Margaret A. Wissman, ExoticPetVet.net, 2006.
- Budgies Grace Pootspete, Tailfeathers Network , 1999-2008.
- Budgies Parakeets and Budgerigars Parrot Parrot, 1997-2006.
- Teaching Your Budgie to Talk No author.
- Millet: Is It Nutritous For My Birds? Alicia McWatters, PhD, CNC.