At this time with brood being observed, I can lay down on ground and call hen (Sallie) to me, then point to ground with finger just above surface and chicks will bolt to my hand and start looking around. When I put my ear close to hen as she does her pointing bit, she appears to be making a snuffling sound that can just barely be made out. When she has her head down like that she can not see potential incoming predators.
Sallie makes tid-bitting (food call) when chicks more than a few inches away reserving the snuffle-sound for when chicks are right next to her head. Rooster (father) makes tid-bitting call to chicks as well but I can not determine if he makes the snuffle-sound. To hear snuffle-sound ear has to be within 18 inches to make it out.