I finally found some pictures of a turkey with a leaking air sac:
http://www.poultrymed.com/Poultrymed/Templates/showpage.asp?DBID=1&LNGID=1&TMID=103&FID=1555
http://www.poultrymed.com/Poultrymed/Templates/showpage.asp?DBID=1&LNGID=1&TMID=103&FID=1555