The Ruby-crowned Kinglet (Regulus calendula) is a very small songbird of the Kinglet family Regulidae native to North America. Both the male and female have olive-grey plumage with a thin black bill and short tail. The male bears a red crown which gives the bird its common name.Their song is a melodious warble and fairly loud, but at least in winter habitat, the most common vocalization is a wren-like scolding "jdit", often repeated several times in close succession. On breeding grounds, they sometimes deliver a prolonged and monotonous "chirrup" call that can be heard for long distances.