[Ask] Chicken Rig

Hi, i have problem when rigging chicken character. my problem is the neck rig. i don’t know how to create the rig for the neck. I want the neck is stretch but when i adding strech rig like

iam getting error with the pole for the neck IK.

https://lh6.googleusercontent.com/-ZuO0eFYy5j0/T_v2W1dfC2I/AAAAAAAADPM/nY_3WqyTlxE/s504/chicken-rig.png

There is my blend file
http://dl.dropbox.com/u/10475540/anak_ayam1.blend

Any idea for solve this problem?