House sparrows were first introduced to the United States in 1851 in New York. They quickly spread, and by the early 1900's, house sparrows were thriving on the west coast. Today they can be found on every continent except Antarctica, with a global population of over 540 million. House sparrows are now the most widely dispersed bird on the planet. House sparrows thrive on the food and shelter that humans provide, whether we intend to provide it or not. They prefer to live anywhere there are people and will nest in all types of structures including signs, gutters, roof eaves, ductwork, attic vents, soffits, you name it. They are aggressive nesters and feeders, commonly driving away native birds such as scrub jays and robins. House sparrows are known to destroy the nests and eggs of other birds, killing the nestlings and even the adults.
Sparrows in small numbers outside are generally not a problem. However, due to their lack of fear of humans, they will often nest and feed inside grocery stores and other buildings. In addition, they can be a problem in eating areas, such as restaurants and cafeterias, particularly in outdoor patios.