Occasionally we run across loose feathers on the ground — sometimes a single feather, sometimes a bunch together (which usually marks the scene of a predator’s meal). Regardless of the situation, the same question always comes up: What species lost these feathers?
The best way to begin is to ignore color and instead study the shape of a feather. All birds share a similar structure, and simple rules will help you determine which part of the bird a feather is from. Knowing that, matching a feather’s color and pattern to a species becomes much easier.
Please note that the Migratory Bird Treaty Act makes it illegal to possess any feather or other part of a native, non-game species. If you find feathers on the ground, it’s OK to handle them, study them, and take photographs, but it is against the law to carry any away with you.
All feathers curve toward the tail, and if you find a feather that is essentially straight, it’s likely to be a tail feather. The largest and stiffest feathers are on the wings and tail, and each of them has a distinctive shape that will allow you to determine exactly which part of the wing or tail it’s from, and (just for fun) which side of the bird.
All of the large wing feathers (primaries and secondaries) curve back and down, and the outermost are strongly asymmetrical: The leading edge is narrower than the trailing edge, and the tip is angled. The inner wing feathers (secondaries) are also curved; the shaft is close to the center of the feather, and the tip is squarish.
The outer tail feathers, like the outer wing feathers, are asymmetrical with a narrow leading edge, and the shaft has a slight S-shaped curve. This shape changes gradually to the almost perfectly straight and symmetrical central tail feathers.
All of the body feathers are smaller, symmetrical, flexible, and rounded. They grow out from the body and curve back toward the tail. The size and length of the feathers varies greatly, from short and stiff feathers around the face and at the leading edge of the wing, to relatively long and flexible feathers on the flanks.
Using these simple guidelines of shape, you should be able to determine the placement of a feather, and then use color to narrow down the possible species.
This article from David Sibley’s “ID Toolkit” column appeared in the May/June 2017 issue of BirdWatching.