At Paul O'Brien's suggestion, I returned to the Rio Pond this PM to closely  
examine the hind toes of the BBWD.  I made digital images from about  fifteen 
feet away with the equivilent of 520mm.
 
Both hind toes appear to be about the same length; neither appears to have  a 
nail.  In fact, it almost looks like a rounded stub on both toes.
 
I checked five reference books to see if there was supposed to be  a nail on 
the hind toe, and could find nothing definitive.  Even in  Kortright's classic 
1942 book "The Ducks, Geese and Swans of North  America."  Perhaps someone 
with access to a skin or detailed knowledge of  the species can resolve this 
question.
 
If in fact there is supposed to be a nail, then I  would conclude that  this 
was a captive duck.  If not, well, then its still up in the air.
 
My image .will be sent to those who want to take a look for  themselves.
 
Bob Mumford
Natural Images Photography
Darnestown
301 948 6813