Cedar shavings gives off fumes that can damage the chicks respiratory system. It is not that the chick immediately falls over dead the instant it breathes the fumes. It is more of a long term effect and it affects some more than others. It is something like your children drinking water that has been in lead pipes. They can drink a little of the water and it really won't affect them, but if they keep drinking the water with lead in it, lead poisoning will eventually affect them mentally and physically.
All cedar gives off the fumes but it is the concentration that causes the problems. I would not hesitate to build a coop out of cedar. Cedar lumber does not give off enough fumes to cause a problem, especially if you have decent ventilation. That's because it does not have the same surface area as cedar shavings. If you take a cedar plank, it has a certain surface area. If you then split the plank, you have the same amount of wood but the surface area has increased a bunch. If you keep splitting that cedar plank until you get down to shavings, it has a tremendous amount more surface area to give off fumes.
Have you ever heard of a cedar chest. It used to be traditional for people to store good clothes in a cedar chest because the cedar fumes kept the moths and other bugs away and protected the clothes. They did not use pine because there is a difference in the fumes pine and cedar give off.
I don't know what those shavings from
Tractor Supply are. They may be pine, aspen or something else. The bag does not say what kind of wood is used. I'm sure the white shavings are not cedar because of the color and the smell. I have seen cedar shavings at
Tractor Supply. The bag is more expensive, the shavings are reddish, and it says cedar on the bag.