Watch the Chicken Pickin' online guitar lesson by TrueFire from Play Acoustic Guitar 8: Advanced Techniques
Chicken Pickin' - Technique #39 is a video guitar lesson presented by Muriel Anderson and is sourced from 50 Right-Hand Techniques You Must Know.
The examples are taken from some licks in the Jerry Reed tune "The Claw."
There are a number of elements working together to get the "chickin pickin" sound. Pulling up a bit on the string to make the string twang (just like we tell you not to do in classical music) is a big part of it.