About 50 species of birds are known to include fresh plant material inside their nests and roosting environment. Increasing evidence indicates that heavy infestation of nests by ectoparasites affects survivor ship and fecundity of breeding adult birds. When ectoparasite build up is high, sea birds and swallows abandon breeding colonies. Certain birds characteristically place green plant material in their nests that is not intended to be part of the nest structure. The secondary compounds of the placed plant material act to reduce pathogens and ectoparasite populations. Several plant secondary compounds are known to function as insect repellants. Some of them act as arthropod juvenile hormone analogs, which delay developmental stages in ectoparasite transition. Birds therefore seem to preferentially select plant species to protect themselves against pathogens and parasites.

Birds such as European starlings ( Sturnus vulgaris), Purple Martins (Progne subis), and American crows ( Corvus brachyrhynchos) reportedly place fresh greenery or aromatic inner bark of western red cedar ( Thuja plicata) in their nests. Greenery use varies geographically within a species.

The rich monoterpene and sequiterpene composition of the volatile oil-bearing plants are shown to be harmful to bacteria, mites and lice. Birds appear to choose the best plants available to fumigate their nests against both microbes and ectoparasites. This they do with their discriminatory ability that can detect specific, volatile, oil-rich plants. In addition to being used for ectoparasite control, these plants also appear to enhance the overall health and weight of the chicks.

House sparrows ( Passer domesticus) bring neem leaves ( Azhadirachta indica) to their nests at breeding time. The leaves contain powerful limonoids—several of which are insecticidal, in addition to being anti-bacterial and anti-fungal. Neem reportedly disrupts egg laying in several plant, animal and human pathogenic parasites. In an interesting observation by biologist Sudhim Sengupta in Calcutta, during an outbreak of malaria, sparrows change to lining their nests with quinine-rich leaves of Caesalpinia pulcherrina (Guletura, Krishnachura). Birds that nest in small cavities like red breasted nuthatch (Sitta Canadensis) apply antiseptic, insecticidal plant resinous secretions around the entrance of the cavity before reusing them.

Even rodents are known to place selected plants in burrows or sleeping nests to possibly act as a fumigant against nest-borne ectoparasites.

“Anting” is another bird behavioral self-help strategy in which they rub crushed ants through their feathers. Sometimes, they let ants crawl over their feather by lying over an anthill with spread out wings. About 200 bird species are known to resort to anting. Birds exclusively use ants that secrete formic acid and such other acrid compounds, which help fight in its ectoparasite defence. It has been demonstrated that anting reduces feather mites in birds resorting to anting. In addition to analgesic formic acid, ants secrete several auxins and β-hydroxy fatty acids that are antibacterial and antifungal. Some bird species are known to rub citrus fruit peel, aromatic leaves, flowers and inanimate objects like naphthalene balls, all of which have antimicrobial, insecticidal property. They are even known to roll in dust and fan out their wings in sunlight to effectively benefit from its UV radiation for sanitation and antibacterial, antiviral effects.