The formula of the toe phalanges was 2-3-4-5-0. The proportions of the toes suggest that they were used for both walking and perching, while the large claws of the thumb and third finger were probably used for climbing. The wing feathers of "Confuciusornis" were long and modern in appearance. The primary wing feathers of a 0.5-kilogram individual reached 20.7 centimetres in length. The five longest primary feathers ("remiges primarii") were more than 3½ times the length of the hand and relatively longer than those of any living bird, while the secondary feathers of the lower arm were rather short by comparison. The outermost primary was much shorter than the second outermost primary, creating a relatively round, broad wing. Its wing shape does not specifically match any particular shape found among living birds. The primary feathers were asymmetrical to varying degrees, and especially so in the outermost primaries. It is unclear whether the upper arm carried tertiaries. Covert feathers are preserved covering the upper part of the wing feathers in some specimens, and some specimens have preserved the contour feathers of the body. Unlike some more advanced birds, "Confuciusornis" lacked an alula, or "bastard wing". In modern birds this is formed by feathers anchored to the first digit of the hand, but this digit appears to have been free of feathers and independent of the body of the wing in "Confuciusornis". According to Dieter Stefan Peters to compensate for the lack of an alula, the third finger might have formed a separate winglet below the main wing, functioning like the flap of an aircraft. Despite the relatively advanced and long wing feathers, the forearm bones lacked any indication of quill knobs ("papillae ulnares"), or bony attachment points for the feather ligaments. Many specimens preserve a pair of long, narrow tail feathers, which grew longer than the entire length of the rest of the body. Unlike the feathers of most modern birds, these feathers were not differentiated into a central quill and barbs for most of their length. Rather, most of the feather formed a ribbon-like sheet, about six millimetres wide. Only at the last one quarter of the feather, towards the rounded tip, does the feather become differentiated into a central shaft with interlocking barbs. Many individuals of "Confuciusornis" lacked even these two tail feathers, possibly due to sexual dimorphism.