David Sibley explains how a bird can change its appearance by rearranging its feathers

BLUE-BLACK AND PALE GRAY: On a cold morning, you might find a Barn Swallow that looks like this one. It has fluffed out all of its feathers, revealing two pale gray patches on the upper side. Art by David Sibley.
BLUE-BLACK AND PALE GRAY: On a cold morning, you might find a Barn Swallow that looks like this one. It has fluffed out all of its feathers, revealing two pale gray patches on the upper side. Art by David Sibley.

Feather color accounts for most of the variation that we see in the appearance of birds, since color fluctuates with age, sex, and other factors, but a bird’s appearance can also change dramatically based on how the feathers are arranged.

Willet provides an obvious example. Its white wing stripe is invisible when the wings are folded, but striking when they are spread. Other examples include the red crown of Ruby-crowned Kinglet and the wing patches of Red-winged Blackbird. They, too, can be hidden entirely beneath other feathers and then dramatically revealed during displays.

Changes in the arrangement of feathers can also cause more subtle changes. Consider Barn Swallow, shown above. When it is alert and active, it usually presses its feathers against the body and shows a uniform blue-black upper side. When relaxed and resting, however, or when fluffed up on a cold day, it will often show two distinct pale patches: a narrow strip along the “shoulder” and a broad pale patch on the lower back.

The band above the shoulder is formed by the bases of the scapulars, the feathers along the margins of the back. The body feathers of nearly all birds are gray at the base and more colorful at the tip. The bases are normally concealed but can be exposed when feathers are fluffed out. The patch on the lower back is formed by long fluffy feathers that cover the sides of the lower back. Usually hidden under the folded wing, they can cover the folded wing when they are fluffed out.

In the Barn Swallow shown here, the fluffed back and flank feathers, along with the drooping scapulars, hide almost all of the folded wing and reveal two light-colored patches that are normally hidden.

A similar pattern can be seen at times in most species of birds. Depending on how much the colors contrast, the effect can be subtle (as in House Sparrow) or striking (as in Olive-sided Flycatcher), but the explanation is the same.

 

This article from David Sibley’s “ID Toolkit” column appeared in the July/August 2014 issue of BirdWatching. 

 

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David Sibley

David Sibley

David Sibley writes the column “ID Toolkit” in every issue of BirdWatching. He published the Sibley Guide to Birds in 2000, the Sibley Guide to Bird Life and Behavior in 2001, and Sibley’s Birding Basics in 2002. He is also the author of the Sibley Guide to Trees (2009), the Sibley Guide to Birds-Second Edition (2014), and guides to birds of eastern and western North America (2016). He is the recipient of the American Birding Association’s Roger Tory Peterson Award for lifetime achievement in promoting the cause of birding and a recognition award from the National Wildlife Refuge System for his support of bird conservation.

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