Size
The size of the bird may help you determine its family or species. The black-throated green warbler is a yellow-breasted bird of approximately 5 inches in length, while the yellow-breasted chat is 7 1/2 inches long. The yellow-headed blackbird is black with a yellow head and a length of 10 inches. Although getting an exact measurement may prove difficult, you may make an estimation to narrow the range of possibilities.
Behavioral Cues
The fan-tail warbler is a yellow-throated bird that walks rather than hops and has a short and weak flight. The rufous-capped warbler has a bright yellow throat and breast and makes a habit of hiding in thick brush. The eastern meadowlark primarily a ground-dwelling bird that is bright yellow from throat to breast with a pronounced "V" in black on the breast.
Head and Eyes
Look for specific details in the head and eyes of the bird to aid in its identification. Compare not only the yellow accents, but other distinctive colors as well. The American goldfinch, for example, is primarily yellow with a black cap. The Bachman's warbler is primarily olive green with a black crown and a bright yellow forehead. The Connecticut warbler has a yellow underside, is primarily gray on top and has bright white spectacles around the eyes.
Body
Look for details in the breast, wings and other aspects of the body to help determine the species of bird. The prairie warbler has yellow underparts with olive upperparts and streaks of brown and reddish-brown. The blue-winged warbler has wings of blue and olive green, but is primarily yellow. The evening grosbeak is a large and stocky finch that is primarily bright yellow with darker head, wings and tail. Minute details may help differentiate similar species.
Tail
The tail is also useful in identification of yellow birds, so look for distinctive qualities in terms of length, shape, color and markings. The pine warbler has a yellow throat and breast, olive-gray accents and a distinctive white undertail. The yellow rail has pale yellow and dark brown stripes and a short black tail. The thick-billed kingbird is a yellow-breasted and yellow-crowned flycatcher with a long, forked, cinnamon-brown tail. The western kingbird is a large flycatcher with a yellow breast, gray and olive upperparts and a long, black tail edged in white.