How did Delia Owens use colloquial diction

The author uses the Southern diction and accents that were common in the rural south of the United States,

“What d'ya mean, where the crawdads sing? Ma used to say that." Kya remembered Ma always encouraging her to explore the marsh: "Go as far as you can --- way out yonder where the crawdads sing."
Tate said, "Just means far in the bush where critters are wild, still behaving like critters.”