Not trying to start any arguments. However I thought I would offer something more about wing trimming. In over 30 years of handling birds. Helping lots of people groom their birds etc I will say that I don't see trimming wings as any way of getting a bird to 'obey' anyone. I know some people think if they trim the wings so the bird can't fly then the bird will depend on humans to move around and have to submit.
In all the years of my experience with captive birds I will say wing trimming will not produce submission to people. Trimming a bird's wings so they cannot fly at all is dangerous for the bird and it will not make the bird submit to people. Birds learn their behavior from other birds, people and their environment.
I am in total agreement with Kathy's statements. Having dealt with re-homed eclectus parrots with clipped wings, one of the consequences is the development of feather destructive behavior as the bird tries every day to "fix" the clipped wing ends. This behavior often becomes habitual and leads to chewing on other feathers on the body. Additionally, birds that have had their wings clipped after their first flight have NOT learned to fly...they haven't learned to turn, to slow down, to land, to rise up, etc. Since there is a "window" of time for them to learn to fly, when this window is closed and their wings clipped, they are then far less able to learn to fly later when their clipped wing feathers have been replaced with full flights. Some can be worked with and learn a little about flight, but I have yet to see one who can become an accomplished flyer. Then there is the problem of loss of bone density. Dr. Scott Echols has written a paper concerning research on the difference in bone density in fully flighted parrots versus wing clipped parrots. Then as Kathy indicates, the respiratory system is also affected. When birds fly, their air sacs are involved in their respiration. We do not clip our birds wings for any reason and we do not recommend it to our clients. There are great training webinars and DVDs which help owners work effectively with their birds so that there should be no reason for clipping wings in order to "control" the bird.
I agree that we should let our birds fly free if we can safely. I have been trimming wings, beaks, toenails over 30 years. I don't like to trim wings. My 'box' on wing trimming is very tight. I never remove feathers entirely and I trim in a way that helps keep birds from reaching a ceiling fan and so they have enough flight feathers so they can land safely without smacking their breast when they land which can cause internal bleeding that is fatal.
Also I never trim a bird's wings so they cannot fly at all. Not ever for any person or price. -- I would like to never trim any bird's wings. However reality is there are millions of birds in captivity. Over 15 million in the USA. Birds are number three most popular pet in the USA. There are millions of bird owners that need help with their birds. They will have their bird's wings trimmed no matter what people say or feel about it. I try to be available to help people learn how to trim wings my way if they are going to trim wings. My way is also the best way for the bird and it's circumstances.