rectrices

Rectrices are the tail feathers of birds, arranged on the tail and playing a central role in flight and balance. They help steer during flight and provide braking and stability; in many species they also participate in display and signaling during courtship or territorial interactions.

The tail is composed of several rectrices, with the exact number and length varying by species. Many passerines have twelve rectrices, but counts range from as few as four to more than ten. Rectrices can be shaped as pointed, rounded, graduated, or forked, and some taxa have elongated outer feathers used in displays.

Structure-wise, each rectrix is a feather with a calamus in the skin and a vane made of barbs. The shaft can be stiff or flexible, influencing tail behavior. In woodpeckers, rectrices are particularly stiff to aid bracing against trunks.

Moult patterns differ among species. In many birds, tail feathers are replaced in a regulated sequence to maintain balance; common schemes include central-to-outward molt or symmetric replacement. Replacement can occur annually or at longer intervals depending on species and environment.

Ecological and behavioral significance includes how tail form affects maneuverability, speed, and stability in different habitats. Some species show sexual or age-related differences in rectrix length or condition, which can aid in field identification and in studies of signaling and fitness.