To pinion or not
I'm going to wade into this debate as a waterfowl keeper of more than 40 years, with a few points:
Waterfowl are more cold resistant if left full winged, as they have not lost part of their insulation on one side
Full winged waterfowl may be physically fitter, as they can exercise by flying
If 'pushed', especially smaller and less intelligent species, pinioned birds will attempt to fly -- one needs to remember this when working with them.
HOWEVER
Pinioned waterfowl can be given significantly more space, because you don't have the logistics and expense of top cover. Full winged geese and swans would be more difficult to accommodate.
No pinioned duck has ever flown into the aviary roof and broken its neck
Almost all waterfowl [and the larger cranes] moult all their primaries at once, and are naturally flightless for several weeks of the year.
Most waterfowl in collections are pinioned, live long and breed well
If one accepts pinioning as a necessary evil, I would suggest it is most acceptable [or least unacceptable] for terrestrial/aquatic subjects, markedly less so for parrots [which are often wing-clipped, though rarely pinioned] and totally unacceptable for vultures [which is sadly too common around the world]
Having said all this, I picked up an injured Turtle Dove in 1971, the end of whose wing actually came off, leaving an effectively pinioned bird that would not normally be in that state. With sensitive treatment, she lived for thirteen years, and left numerous descendants. Her daughter lived to be nineteen, and I still have her granddaughter who is nearly that age. Obviously one would not pinion or wing-clip a dove, but this wild casualty's history might demonstrate that sensitively kept animals do not brood on the shortcomings of their lives, but just get on with it.