The smallest North American tern (length 21-24 cm); breeding adult is mainly gray above, with a black cap and nape, white forehead, black line running from the crown through the eye to the base of the bill, orange-yellow bill often with a dark tip, white or grayish underparts, short deeply forked tail, and yellow-orange legs and feet; a black wedge on the outer primaries is conspicuous in flight (NGS 1983). Adult in winter plumage has a dingy cap, dark nape, a black line through the eye, a dark bill, and yellowish feet and legs (NGS 1983, Peterson 1990). Juvenile is pinkish-buff above, with brownish U-shaped marks on the back; crown is dusky; dark bar is present on the front part of the folded wing. First-summer birds resemble adults but retain the dark bar on the wing and have a dark bill and dark feet and legs, dusky primaries, a dark nape, and a black line through the eye (NGS 1983, Forbush 1927, Farand 1983). <br><br>VOCALIZATIONS: a shrill "zreep" and a harsh "kip, kip, kip." <br><br>EGGS: pale or olive buff with dark purplish-brown or blue-gray speckles and streaks. Seventeen eggs from Illinois averaged 31.2 X 23.8 mm (Hardy 1957).