They are probably more troublesome than starlings in some ways. Small cavity-nesting species like chickadees, titmice, wrens, bluebirds and purple martins can fit through a cavity entrance too small to admit a starling. However, the smaller house sparrow is not excluded. House sparrows tenaciously claim bird houses and other cavities and will pierce the eggs and kill the nestlings of other species prior to taking over a cavity. Their bulky nests are sometimes built atop the remains of the former tenant's nest - or the former tenants themselves.
House sparrows can be a problem in bluebird or martin houses.
Houses should be checked and house sparrow nests and their contents cleaned out. A house put up for bluebirds or martins and allowed to produce generation after generation of house sparrows is doing more harm than good to its intended tenants. House sparrows can also dominate bird feeders. Bread or bread crumbs and millet are foods to avoid when house sparrows are a problem. Because they are aliens, neither the European starling nor house sparrow are federally protected, as are virtually all other birds.