Here is a quiz with three very different wings, and a detailed explanation follows (don’t peek).
With thanks to the online wing collection of the Slater Museum of Natural History, University of Puget Sound for allowing the use of these photos.
Quiz 19: All wings are the same?
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Wings come in a tremendous array of sizes and shapes, but they all share the same basic structure. The primaries are the long feathers that form the wingtip, and are attached to the “hand” bones. The secondaries are the big feathers forming the inner part of the wing, attached to the “arm” bones. Each of these big flight feathers has a greater covert, and each greater covert has a smaller median covert, and so on up to the very small coverts at the leading edge of the wing.
The three species shown here – Black Skimmer, Allen’s Hummingbird, and Northern Flicker – all have ten primaries (the outermost primary on the flicker is very small and nearly hidden). The secondaries always differ slightly in shape and color from the primaries, and you can probably guess where the change happens just by looking. To confirm, try counting the ten primary feathers back from the leading edge of the wing, and you will be able to see the subtle shift to the secondaries.
The number of secondaries is much more variable. Small land birds like flickers have about ten (passerines have nine), hummingbirds (with a very short “arm”) have only six, while long-armed species like Black Skimmer can have twenty or more.
To understand wings and appreciate the differences more, try studying these three wings and thinking about the things they all have in common.