Whether fleas or mites (which is most likely mites as TC said) if it is available for use in your state Sevins dust will take care of both. Make sure to dust both the chickens and coop area. If possible keep quarantined from your other birds as mites can spread quickly from bird to bird. We have horrible sand fleas where I live and while I've seen them in the coops, I've never seen them on the birds. Someone else may have had a different experience though so bear in mind this is all IMHO! Good luck!
