Ornithonyssus sylviarum is a haematophagous ectoparasite of poultry. In both size and appearance, it resembles the red mite, Dermanyssus gallinae. They primarily infect egg laying chickens. They contribute to economic damage and feed on their host's blood which leads to lowering the egg production and feed conversion efficiency. Anemia or death can be an effect of a high amount of infestation within the birds. While they mainly do target wild birds they can also become permanent ectoparasites in the domestic poultry. The main nesting sites are generally in a close proximity to poultry coops.