Appearance
While many different bird species feature heavy yellow colorations, there are relatively few that are completely yellow. American goldfinches have very large areas of bright-yellow feathers, broken up by sharply, juxtaposed swashes of black and white, for instance. The common yellowthroat has fewer bright-yellow spots, but they are still prominent and relatively unmuddled. The yellow warbler, on the other hand, has chestnut colorations mixed in with their yellow feathers.
Geography
Yellow birds occupy many areas of the world, from warm, temperate climates to those bordering more frigid areas. Take the yellow warbler, for instance. This bird is found in the northern two-thirds of North America, including parts of Alaska and Canada. It is also found in central Mexico and Central America. The golden conrue, on the other hand, is found only in small areas of rain forest in Brazil.
Habitat
Yellow birds are also found in a variety of habitats. The Brazilian golden conrue, for instance, is found in dry rain forests, rather than the moister tropical rain forests. Yellow warblers are birds more suited to wet habitats, particularly deciduous thickets that contain various species of willow trees. Yellow goldfinches have less specific habitats, being common in a variety of temperate North American habitats. The common yellowthroat, also found throughout North America, is particularly suited to marshes, stream-side thickets and other wetland areas.
Gender Variations
Gender is an important attribute that affects the exact yellow color an individual bird is going to have. In general, males have a brighter yellow color in order to attract mates. Females tend to have either a darker or paler yellow color. Female yellow goldfinches, for instance, have a more faded yellow color, but no difference from males in black and white markings on the head and wings. The common yellowthroat is a bit different in that males and females have similar shades of yellow. The difference between them is the male's black mask around the eyes and beak.