Small hummingbird of desert habitats in Southwest U.S. and western Mexico. Compact and short-tailed with a slightly drooping bill. Male has a brilliant purple crown and throat that extends down to a point on each side; the purple coloration can appear black in poor lighting. Females are plainer with greenish back and dingy grayish underparts. Females similar to Anna's Hummingbird, but smaller, short-tailed, and have a drooping bill. Costa's is paler below with less green flecking on belly; its shorter tail is as long as the wings when perched. Anna's tail tip extends below wingtips.