The distance that a bird's longest primaries extend beyond its longest secondaries (or tertials) when its wings are folded is referred to as the primary extension or primary projection. As with wing formulae, this measurement is useful for distinguishing between similarly plumaged birds; however, unlike wing formulae, it isn't necessary to have the bird in-hand to make the measurement. Rather, this is a useful relative measurement—some species have long primary extensions, while others have shorter ones. Among the Empidonax flycatchers of the Americas, for example, the Dusky Flycatcher has a much shorter primary extension than does the very similarly plumaged Hammond's Flycatcher. Europe's Common Skylark has a long primary projection, while that of the near-lookalike Oriental Skylark is very short.
Read more about this topic: Flight Feather
Famous quotes containing the words primary and/or extension:
“Wilful sterility is, from the standpoint of the nation, from the standpoint of the human race, the one sin for which the penalty is national death, race death; a sin for which there is no atonement.... No man, no woman, can shirk the primary duties of life, whether for love of ease and pleasure, or for any other cause, and retain his or her self-respect.”
—Theodore Roosevelt (1858–1919)
“The motive of science was the extension of man, on all sides, into Nature, till his hands should touch the stars, his eyes see through the earth, his ears understand the language of beast and bird, and the sense of the wind; and, through his sympathy, heaven and earth should talk with him. But that is not our science.”
—Ralph Waldo Emerson (1803–1882)