Make sure you not calling right in their face. Focus on wing tips and tails. I would say more of a cover issue as you did up a make shift blind. Try just a simple series of consistent quacks than a set note system. Focus on keepin there attention, use the notes when they are banking. And a jerk string or motion in general in the spread is more important than calling in my opinion.
THE RIGHT OF THE PEOPLE TO KEEP AND BEAR ARMS SHALL NOT BE INFRINGED
YOU GOT A PERMIT TO ASK STUPID QUESTIONS LIKE THAT (TRACE ADKINS)