Pat,
The easiest par 3 to birdie may be 16, especially with the middle to back left pin.
Not in the aggregate. #12 had 59 birdies this year, compared to 41 for #16. Sure, there may be a pin or two that is easier to go at, and thus open the hole up to birdies, but this year's statistics suggest #16 has only one of those. Day-by-day birdies at the two holes:
#12: 13-19-15-12
#16: 3-25-5-8
So only day -- Friday -- was #16 easier to birdie, and that by only six birdies. #12 was far easier to birdie the other days.
But that, I think, is primarily a function of the two greens, which are drastically different -- one skinny and small, with probably only four decidedly different pin positions, and one rather large, deep, and full of contour, with some difficult pin positions in which to get the ball close.