They are the cockatiels and Quakers, both of which I own. Most everyone is familiar with the beloved cockatiel. With its jaunty crest perked up in interest, this comical bird comes in many mutations, such as lutino and the new emerald and olive colors. The care of a cockatiel, is much like a parrotlet, with a large cage being a must. Tiels, as they're called, can be prone to obesity, so a good pellet diet or a low fat seed diet supplemented with fresh fruits and vegetables and lots of exercise is vital.
Cockatiels are very personable and quickly learn various whistles and to say a few words.
Their toys are inexpensive, and they are a great addition to any family. Quakers, or monk parakeets, are another great intermediate bird. However, they are illegal in some states, so check with other bird breeders or the authorities to determine if they're legal where you live. The normal Quaker has a gray face and chest with a green back and a long, green tail. There is a blue mutation that is also available, and it is more expensive than the normal green.