This phrase is used by inbreds or hicks to replace the phrase "quarter mile time" when racing. Usually used by the inbreds when racing a POS truck against another POS truck. Imagine street racing without the city and out by a old barn and corn field.
"Hey Cletus, what your bird to sign time on that big ol' truck you have been haulin' that hay with?" "It's about 7.8 seconds I reckon." "Well shit, I suppose you would beat in my John Dear green tractor." "Damn straight, I'm packin' a 350 hemi supercharger in this bitch." "Your shittin me?"