What Birders Should Know About Wing Feathers

Wing patterns may seem complicated at first glance, but the good news is that the arrangement of wing feathers in all types of birds is quite similar (and is nearly identical in all songbirds). So, learning about a bird’s feathers will unlock a wealth of information about other species.

Of all the feather groups that birdwatchers talk about, the wing coverts are one of the most important. They are easily identified and often have distinctive patterns, and once you locate them they provide a reference point for understanding other details of the wing pattern and structure.

Functionally, wing covers help streamline the wing during flight by covering the base of the large flight feathers to form an airfoil shape. The coverts are lined up in rows, starting with tiny feathers along the leading edge of the wing and rows of increasingly larger feathers further back. The largest wing coverts (the greater coverts) are in the middle of the wing and overlap the base of the greater flight feathers. The next row forward (called the median coverts) is made up of smaller feathers and overlaps the base of the greater coverts. The next row is made up of smaller feathers (lesser coverts), and these continue in smaller and smaller rows to the leading edge.

Another view of a Chipping Sparrow, with the greater coverts shown in blue. Artwork by David Sibley

When the wing is folded, the greater coverts form a roughly diagonal area around the middle of the folded wing. Only the long flight feathers extend behind them. The smaller coverts, arranged in front, are often hidden under the downy feathers of the body. One thing that helps distinguish blankets from body feathers is their texture. The body feathers are loose, downy, broad and curved, while the coverts are stiff, narrow and flat. Even when the feathers of the rest of the bird move, the arrangement of the wing feathers remains more or less the same.

Once you locate the greater blankets, you can learn a lot by studying the details of their colors. The wingbars are formed by the pale tips of the greater and median coverts. Some species have broader pale tips on the greater coverts, others have broader tips on the median coverts, and some have only a single pale wingbar. Some species have a pale margin along the entire length of each concealed feather, others do not.

Like any in-depth study, focusing on one detail like the wing coverts can lead to insights into other details and a better understanding of the bird as a whole.

A version of this article originally appeared in the May/June 2019 issue of BirdWatching.