Unlike poultry mites that are arachnids, these tiny white lice are considered insects. If they take up residence on your chicken's body, they live off they're dead skin, dried blood, and feathers. They spend their lifetime on the body of the host chicken, laying it's eggs among feather shafts.
Here are two common types of lice that affect chickens:
Poultry body lice are the most common lice to bother backyard flocks. They congregate around the vent area, the breast and the thigh areas of chickens. They generally lay their eggs at the base of feathers around the vent area. They lay their eggs in clusters.
These lice are a bit smaller than body lice. They lay their eggs at the base of the feather shaft or along the barb of the breast or thigh feathers. They lay their eggs individually instead of in clumps like the body lice do.
With any lice infestation, the symptoms are the same. Lice irritate chickens and you'll notice them picking themselves and grooming excessively.
Prevention and Treatment
Lice are primarily introduced to the flock through other animals, such as bringing new infected hens into your flock or wild birds that leave their droppings in chicken areas. Checking new birds thoroughly before mixing them with your chickens will help, but it doesn't guarantee lice-free hens.
Keeping bedding clean is important and allowing the birds proper areas for dust bathing will help.
Also, it's good to check your hens for lice eggs at least twice a month. If you find eggs, scrape them off the hen and burn them (or flush them down the toilet). As a preventative measure, some chicken owners occasionally dust their chickens with a poultry dust that treats lice on chickens. Be careful to follow the directions on the product for best results.
ORGANIC LICE TREATMENT:
If you're like me, you welcome organic treatments whenever you can get them. A safe and affective way to treat lice in your chickens without harmful powders (and giving up your eggs for at least two weeks) is by giving your chickens a two part bath.
First, bathe your chickens in Dawn dishwashing soap and water, being careful to keep their head from getting wet (but make sure you wash up in their neck, as that's one of the places lice like to hang out). Next, rinse them in water mixed with apple cider vinegar.
This treatment effectively kills lice, however it doesn't kill the nits. So, you need to repeat treatment 7-10 days later to make sure ALL the lice are gone.
Along with this treatment, clean out the chicken coop thoroughly and wash down with a non-toxic cleaners such as Simple Green. Make sure to get cracks and corners and roosts and nest boxes. Once dry, sprinkle coop with diatomaceous earth before adding bedding (go light on the bedding, as just like the bathing, this part will need to be repeated in 7-10 days as well.)
I've personally used this treatment for lice on my chickens and it works well.
Here's more information on other common chicken problems.
Learn about poultry mites here. And how to treat them.