The hen flea ( Ceratophyllus gallinae ) is the most common flea in their nests . The small , pale house @-@ sparrow flea C. fringillae , is also occasionally found there and probably arise from the habit of its main host of taking over the nests of other species . This flea do not occur in the US , even on house sparrows . Lice include Menacanthus eurystemus , Brueelia nebulosa and Stumidoecus sturni . Other arthropod parasites include Ixodes ticks and mites such as Analgopsis passerinus , Boydaia stumi , Dermanyssus gallinae , Ornithonyssus bursa , O. sylviarum , Proctophyllodes species , Pteronyssoides truncatus and Trouessartia rosteri . The hen mite D. gallinae is itself preyed upon by the predatory mite Androlaelaps casalis . The presence of this control on numbers of the parasitic species may explain why birds are prepared to reuse old nests .