4 Day old chick with pulsating butt

[solomine]

I have a 4-day old little brahma chick that has a pulsating butt (even her tail moves a tiny bit). Her vent doesn't open and close but it looks like she's either breathing hard or straining hard. She's slightly less active than the rest of my chicks, but can walk around normally and is getting water.

Should I be worried or is this normal behavior? It looks like she might have constipation (she does not have any poop stuck to her butt either. It's completely clean!)

I did recently change my chicks' bedding from paper towels to pine shavings... but that shouldn't be related.. or could it be?

 

[Judy]

My first thought was constipation, but when you said the vent is clean, I have to ask, has this chick ever pooped? You can try a little molasses in the water as a laxative. If it were mine, I'd separate it for a few hours just to find out if it is pooping. It is possible that it has no open passageway for the poop to come out.

 

[Lazygaze]

What happened? Mine is doing this