Most of the parakeets you find in the Petshops are what are called American parakeets as they are color mutations of the original Grass Parakeet or Budgerigar from Australia. They are similar in size and appearance to the original birds imported from Australia.
Occassionally you will find what are called English Budgerigars for sale in those shops. These are genetically the same as the regular parakeet, however they are almost twice the size of your average keet. These birds were developed and bred for show purposes. However they can be tamed and taught to talk just as readily as the regular parakeet.
Parakeets in the wild are colony type breeders, and thus you do need two to three pairs to stimulate them to breed, along with greens and sprouted seeds. They will call to each other and chatter as long as there is light around them. If you are going to breed them in an aviary type situation you want to provide at least one more nest box than pairs and have them all at the same height to prevent fighting for nesting spots. However, you will not be able to be positively be sure of the parentage of the birds this way. If you are breeding for a specific color or pattern then you will want to cage breed them and keep them one pair to a cage.
In taming a single keet, it is best to have just the one bird without the distraction of others, as has been already suggested. Studies have shown that a low soft voice, such as a childs or a womans, gets the best results in teaching them to talk. You can get training cd's or tapes at most pet stores.
For more information on Parakeets or Budgerigars you can check out the ABA (American Budgerigar Association) or the BAA (Budgerigar Association of America) websites.
Cockatiels are also native to Australia, for more information on them got to the NCA(National Cockatiel Association) website.
Zebra Finches are another Australian Native and do well in groups of 6 or more. For some reason, 1-4 birds do not do well, as they are social little things and seem to be able to count up to 4, once you have 5 or more the aggression between the males and females goes away seemingly, as the males are distracted by the other birds. They are prolific breeders once started.
