How can lice damage the feathers of heavily infested birds?

Chewing lice—specifically those belonging to the suborders Amblycera and Ischnocera—are parasitic insects that live on birds and feed directly on their feathers, skin, and occasionally blood.123

In cases of heavy infestation, these insects can cause severe damage to a bird's plumage. While the lice themselves consume feathers, the irritation they cause often leads the host to scratch or peck at its own body in an attempt to find relief, which further exacerbates the damage to the feathers and skin.31

Birds that are already sick or possess damaged bills are particularly susceptible to these heavy infestations because they are unable to perform the necessary grooming and preening required to keep louse populations in check. Beyond physical damage to feathers, such infestations can lead to secondary infections from scratching and may negatively impact the bird's overall health, including reduced egg production and hindered fattening in poultry.4123