The cheery and sociable house sparrow is more closely associated with humans than any other widely established North American exotic. Introduced to New York City in 1851, the species today flourishes in both large cities and remote agricultural outposts—just so long as there is some trace of human influence. It aggressively defends nest cavities, possibly to the detriment of native species. It is more gregarious in winter. Polytypic. Length 6.3".

Tame; gregarious. Flight more direct, often higher, than native sparrows. Bill thick, conical; legs short; stocky build. One molt per year, but seasonal variation pronounced. Adult male: worn (breeding) male contrastingly marked; throat and breast black, postoccipital and nuchal regions chestnut, wings russet. On freshly molted (nonbreeding) bird, the blackish and