Subject: HOW do substances remove stains (specifically dirt/handoils from feathers)?

I am doing a science project on "What non-harmful substance removes dirt/oil 
from a bird's feathers the best?"  There are two cockatoos at the Brevard Zoo 
that have very discolored backs, and I want to help the zookeepers find 
something that they can use (wipe on/ lightly rinse off) to clean the birds, as 
opposed to the process they use for removing oil from oil spill birds, which is 
to soak the feathers with straight detergent.  The problem with this is that it 
removes ALL the oils from the birds feathers, and the feathers lose their 
waterproofing and some insulating abilities for awhile.  The substances I'm 
testing are things like: white vinegar, citrus oil, primrose oil, lemon juice, 
baking soda paste, cornstarch, etc.  What I would like to know, is the science 
behind the dirt/grease removal.  If I find something that works, HOW does it do 
it?  There must be some breaking down of enzymes or something, and in the case 
of breaking down the oils from peoples hands, what is really happening there?  
I have searched your libraries, but I didn't really find the "HOW" I want to 
know about... I did find one entry that talked about using biological enzymes 
to remove greasy spots.  HElp, please!

Re: HOW do substances remove stains (specifically dirt/handoils from feathers)?