query: What is the smallest species of bird?
passage: Bee hummingbird
The bee hummingbird, zunzuncito or Helena hummingbird (Mellisuga helenae) is a species of hummingbird which is the world's smallest bird.[2][3] It is endemic to Cuba and the Isle of Pines.
passage: Bristlebird
Bristlebirds are long-tailed, sedentary, ground-frequenting birds. They vary in length from about 17 cm to 27 cm, with the Eastern Bristlebird the smallest, and the Rufous Bristlebird the largest, species. Their colouring is mainly grey with various shades of brown, ranging from olive-brown through chestnut and rufous, on the plumage of the upperparts. The grey plumage of the underparts or the mantle is marked by pale dappling or scalloping. The common name of the family is derived from the presence of prominent rictal bristles - three stiff, hair-like feathers curving downwards on either side of the gape. This feature distinguishes them from the scrub-birds, to which they are similar in appearance although not closely related. The bristles, which are conspicuous in many birds that like the bristlebirds forage for insects in dark locations, may serve a tactile function in locating or manipulating prey.