Breeding season for house sparrows begins early in the spring and sometimes even in midwinter. They are very prolific with each pair producing up to four broods a season. House sparrows are nonmigratory and are so closely tied to human activity that they are only found in the vicinity of human habitation.

House Sparrows are very aggressive and are the number one reason for the decline in the Purple Martin and Eastern Bluebird in our eastern and southern states. In Montana they are responsible in part for the decline of other cavity nesting birds. The aggressive nature of the House Sparrow also results in their driving away more desirable song birds from feeders and other locations. Most House Sparrow damage is related to their nesting and feeding habits. They are very gregarious, nesting and congregating in large numbers. In these situations they are a considerable nuisance, and often cause unsanitary or odorous conditions. Droppings can kill ornamental vegetation and damage finishes on vehicles. House Sparrows are also a factor in the spread of several diseases such as chlamydiosis, New Castle disease, salmonellosis, toxoplasmosis and transmissible gastroenteritis. House Sparrows also carry parasites, insects, fleas, mites and fowl ticks.