brown leghorn moving head back and shaking it side to side

[mehzibus]

She's been laying for about one month. Very healthy, free range. For a couple of weeks she's been displaying this behaviour a couple of times a day : tucking her head back into the top of her back, and wagging her head from side to side a few times, then back to normal. She is not doing this behaviour specifically for me, because I've spied on her, and she'll do it regardless. No signs of anything else out of the ordinary. Any ideas, anyone ?

 

[Den in Penn]

Only two things come to my mind. One is she is having a hard time swallowing for some reason. Or its a behavioral tic.