Numbers of feathers (from Chaplin, S. and J. Faaborg. 1988. Laboratory Manual and Field Exercises. Ornithology: An Ecological Approach. Prentice-Hall, Inc., Englewood Cliffs, NJ):

• Primaries - "Most birds have 10 primaries, but . . . grebes, strorks, and flamingos have 12, herons, ducks, and gulls have 11, and several families of Old and New World passerines have 9."
• Secondary remiges - "The number of secondary remiges is even more variable, ranging from 6 to 32, and is a result of variability in the length of the forearm (ulna). Hummingbirds have the fewest secondaries (6), most passerines have 9 (rarely 10 or 11), while vulture species have 17 to 21, and albatrosses up to 32."
• Alula feathers - "The number of alula feathers varies from only 2 quills in hummingbirds to as many as 5 or 6 in some cuckoos. In most passerines, they number 3 or 4 . . ."
• Rectrices - "Most birds have 12 rectrices (6 pair), although there are many exceptions. Hummingbirds, swifts, most cuckoos, motmots, and toucans have 10, some rails and grebes have 8, and a few very small tropical passerine birds have 6. On the other hand, a few species that utilize their tail feathers as part of their sexual display have more than 12: for example, ptarmigan (16), prairie chicken and Ring-necked Pheasant (18), male peafow and Blue Grouse (20)."

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