Funny you should bring up Quakers, as I just got one this past Saturday.
I did a lot of research before getting my Q and all though I'm a new
owner, I feel I learned a lot.
 
It's not just the ferrets you have to worry about causing trouble, but
also the Quaker!  Quakers are territorial and can be very jealous of
other people or animals that take your attention away.  They also think
they are the size of a elephant, as they are fearless and will take on
animals 50 times their size.  In my opinion, it would not be enough to
just clip the wings or to train the fuzzies to ignore the bird.  Quakers
WILL make a effort to attack other animals, such as climbing down their
cage or if really determined, they will fly off despite knowing they
can't fly.  If the ferrets come up to the cage and put their nose or feet
up against it, don't be surprised if the Quaker attacks what they
can-it's common for them to be very cage territorial.
 
My ferrets have their own room and I have found this to work out the best
for my lifestyle.  However, I don't think it is impossible to have a Q
and ferrets if you are willing to take the percautions needed.  I would
never leave the ferrets and Quaker out at the same time, even when home.
Give each their own seperate playtime.  Watch the Qs cage carefully for
the fuzzies exploring too close...don't want them to loose a toe or
nose. <G>  If needed, set up some plexi glass towards the bottom half of
the cage to protect both parties.
 
And lastly, research! :)  There is a excellent book called Guide To The
Quaker Parrot by Mattie Sue Athan.  This book goes well into the down
side of quakers, as well as the up side they have!
 
Good luck! :)
[Posted in FML issue 3876]