**House Sparrows** (*Passer domesticus*) are small, robust, invasive birds introduced to North America from Europe in the mid-1800s. They are highly adaptable, urban-dwelling birds found nearly everywhere humans live. While they are a familiar part of the urban landscape, they are considered structural, health, and agricultural pests due to their aggressive displacement of native birds, excessive noise, consumption of stored grains, and the sanitation issues caused by their messy nests and droppings.
Taxonomy and Classification
House Sparrows belong to the family Passeridae. They undergo complete metamorphosis (egg, fledgling, adult). They are non-migratory and highly opportunistic generalists, which has allowed them to rapidly colonize new environments. House Sparrows are **not** protected under the Migratory Bird Treaty Act in the U.S. because they are non-native.
Physical Description
House Sparrows are small, chunky birds, about 5 to 6 inches long.
- **Male:** Distinctive gray crown, black throat/chest patch (bib), white cheeks, and a reddish-brown stripe behind the eye.
- **Female:** Plain, dull brownish-gray, with an unstreaked breast and a pale stripe over the eye.
- **Nests:** Large, messy, dome-shaped structures built haphazardly of straw, trash, feathers, and various debris. They are typically stuffed into crevices, eaves, roof vents, or inside building signs.
- **Droppings:** Voluminous, often concentrated under roosting and nesting sites, causing fouling of equipment and sidewalks.
Distribution and Habitat
House Sparrows are now one of the most widely distributed birds in the world, absent only from cold Arctic regions. Their habitat is closely associated with human activity—cities, suburban parks, farms, and transportation hubs. They prefer nesting in man-made structures over natural cavities.
Behavior and Conflict
House Sparrows are highly aggressive and reproduce prolifically, having 3–5 broods per year.
- **Displacement of Native Birds:** They aggressively usurp the nests and territories of native cavity-nesting birds (like bluebirds and swallows), often killing the native adults or destroying their eggs/young.
- **Structural Damage:** Nests built in vents, gutters, and commercial signs cause clogging, fire hazards, and corrosion due to droppings.
- **Food Contamination:** They cause significant economic damage in agricultural settings and feed stores by consuming and contaminating livestock feed and stored grains.
- **Health Risk:** Their droppings can harbor bacteria and fungi, posing a risk of diseases like Histoplasmosis, though the risk is usually low outside of heavy infestations.
Management and Prevention
Control must focus on exclusion and source reduction, as they are not protected.
- **Exclusion (Key):** Screen all building openings, vents, and eaves with hardware cloth or specialized bird netting to prevent access to nesting sites.
- **Nest Removal:** Repeatedly and routinely remove nesting material from crevices and cavities every few weeks to discourage the birds from establishing territory.
- **Deterrents:** Install roosting prevention products (bird spikes, netting, or specialized wires) on ledges and beams where they congregate.
- **Source Reduction:** Eliminate outdoor feeding opportunities, such as securing garbage cans and cleaning up spilled birdseed (especially millet and corn).
Conservation and Research
House Sparrows are managed as an invasive exotic pest. Research focuses on methods to protect native bird species from sparrow aggression and developing better, humane exclusion techniques in urban environments.