Bird feathers will surely not trigger large areas of moire, since they are somewhat irregular, as Thom has pointed out. It will likely be more like speckles and a few lines of wrong color, maybe not very visible, but wrong nonetheless.

Thom Hogan also qualified his comments that it should be rare to get moire that is plainly visible in the final image. You may get small color errors in many places that are not very apparent.

Tom
Bay Area Nikonian

http://www.tkphoto.me/