Hummingbird
Hummingbirds are birds native to the Americas and constitute the biological family Trochilidae. They are among the smallest of birds, most species measuring in length. Indeed, the smallest extant bird species is a hummingbird, the bee hummingbird weighing less than .
Goldcrest
The goldcrest is the smallest European bird, in length, with a wingspan and a weight of . It is similar in appearance to a warbler, with olive-green upper-parts, buff-white underparts, two white wing bars, and a plain face with conspicuous black irises. The crown of the head has black sides and a narrow black front, and a bright crest, yellow with an orange centre in the male, and entirely yellow in the female; the crest is erected in display, making the distinctive orange stripe of the male much more conspicuous. The small, thin bill is black, and the legs are dark flesh-brown. Apart from the crest colour, the sexes are alike, although in fresh plumage, the female may have very slightly paler upper-parts and greyer underparts than the adult male. The juvenile is similar to the adult, but has duller upper-parts and lacks the coloured crown. Although the tail and flight feathers may be retained into the first winter, by then the young birds are almost indistinguishable from adults in the field. The flight is distinctive; it consists of whirring wing-beats with occasional sudden changes of direction. Shorter flights while feeding are a mix of dashing and fluttering with frequent hovering. It moves restlessly among foliage, regularly creeping on branches and up and down trunks.