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What to look for as birds molt their worn-out feathers

molt
Here are two views of the sixth primary of a Ring-billed Gull. It’s freshly grown in the fall (upper) and very worn in the late summer of the following year (lower). Art by David Sibley

Late summer is the time of year when many birds replace their feathers in a process called molt. Old feathers, most of which have been worn for about a year, fall out, and new feathers grow in their place. Gulls, for example, molt their wing feathers only once a year, and we generally don’t notice any change in their appearance. The color and pattern of their wings remain the same all year. After a year of constant wear and exposure, it’s amazing that feathers still function, let alone retain essentially the same appearance.

If you are at the beach at this time of year, you will probably find feathers on the sand. Virtually all of these will be old feathers, “used” by the birds for up to 12 months and then dropped in the normal process of molt. Among them you might find large wing feathers dropped by gulls. It’s illegal to keep these feathers, but you can pick them up and examine them.

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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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