BROWN THRASHER
The tail of a bird is formed of an equal number of feathers in pairs, most often twelve. When spread they are the shape of a fan ([Fig 13]), and when closed they lie over each other with the middle pair on top.
Fig 15.
Tail of Swallow-tailed Kite.
The tail feathers are not always of the same length, and that makes a difference in the shape of the end. Sometimes they are even (like Fig. 14), when the tail is said to be "square." Sometimes the middle feathers are a little longer than the outside ones, and then it is "rounded" or "pointed." If the outside feathers are longest, the tail is "forked" ([Fig 15]).
The feathers of the tail are called rectrices, or "rudders," because they are supposed to be used to steer, or direct the bird's course in flying. But the tail is used also as a brake to check the speed in alighting.
The tail is used more than any other organ to express the emotions. Some birds, like the catbird and thrasher, keep it moving nearly all the time, jerking it this way and that, and tossing it upward.