Patches in birds’ tail feathers can trick you into identifying them

Many birds have white spots on their tails, and the shape of these white spots can be a very useful identification clue. But they look different from above and below, and they change dramatically as the tail opens and closes.

Understanding tail mechanics and the arrangement of tail feathers is key to understanding the changing appearance of these white spots.

ONE TAIL, THREE VIEWS: The tail of a Dark-eyed Junco seen from below when closed (top) and from above when closed (middle) and open (bottom), with central rectrices in darker brown. Artwork by David Allen Sibley

The tail is basically a fan, with long straight feathers in pairs left and right. When the tail is open, the feathers fan out to form a wide triangle. When the tail is closed, the feathers stack on top of each other (roughly in left and right stacks); the outermost feathers slide underneath to form the bottom of each stack, and the central tail feathers are on top.

When the tail is closed (all feathers stacked) and viewed from the side or above, one sees mainly the central tail feathers and the outer edge of each of the other feathers. Viewed from below, the outer tail feathers are fully visible at the bottom of the pile.

The white tail spots are always on the outer tail feathers and the central tail feathers are always dark. On species with white tail patches, this means that the closed tail when viewed from above or from the side appears all black (the dark central tail feathers) and when viewed from below appears partially or entirely white (the outer tail feathers).

Keeping this arrangement of feathers in mind will help you understand the changing appearance of tail patterns. Watch it on familiar species to improve your birding skills.

This article first appeared in the November/December 2020 issue of BirdWatching magazine. Subscribe now.

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