The prothonotary warbler (Protonotaria citrea) is a small songbird of the New World warbler family. It is named for its plumage which resembles the yellow robes once worn by papal clerks (named prothonotaries) in the Roman Catholic church. The prothonotary warbler is 13 cm (5.1 in) long, weighs 12.5 g (0.44 oz), and has a wingspan of 22 cm (8.75 in). It has an olive-coloured back with blue-grey wings and tail, yellow underparts, a relatively long pointed bill, and black legs. The adult male has a bright orange-yellow head. Females and immature birds are duller and have a yellow head. In flight from below, the short, wide tail has a distinctive two-toned pattern, white at the base and dark at the tip. (Source: Wikipedia.org, CC BY-SA)