Chicken mites?

[annaBsChick]

It depends on which mites they are. If they're mites at all. Here is a good infographic on how to figure it out - http://www.poultrydvm.com/featured-infographic/identifying-common-ectoparasites-of-backyard-poultry

 

[Al Gerhart]

Bingo, that is how I always checked for mites, around the vent, and was always taught to get the dust inside the cracks and crevices as mites hid during the day.