If you bird seems rumpled, restless and have what appears to be a dirty vent, it is time to take a look and inspect them for lice. Lice are transparent and become golden or cream colored as they age. They lay and "glue" their white eggs to the base of feathers, usually in the vent area or under the wings. They are easily seen by the naked eye, especially at the vent area. They are most prolific in fall and winter and at the time of molt since they feed on dead/dry feather and skin cells which are more common during molting season. Lice spend their entire life cycle on the bird and can't survive off the bird for more than about a week.
Who: All birds; especially:
When: Any age bird can have them since often the transmission is from hen to chick, or from wild birds to domestic flocks.
Why: Contact between birds, often between hen and chicks
Affects: Skin, feather shafts and vent area
Clinical Diagnosis: Diagnosis is made through visual inspection of the birds skin, feathers and vent. Lice and nits (eggs) are visible to the naked eye.
Parasites with similar symptoms: Mites, ticks and fleas.
Duration of symptoms: The symptoms will generally continue until the infestation is treated. Birds can sometimes self-treat if afforded a good location for dust bathing.
Morbidity: High. It spreads by contact between birds.
Mortality: Low. Higher in young or sickly birds.
Transmission to people: Chicken lice may crawl onto humans, however they cannot survive since humans do not provide a food source for this species of lice.
Damerow, Gail. The Chicken Health Handbook: A Complete Guide to Maximizing Flock Health and Dealing with Disease. North Adams, MA: Storey, 2015. Print.