. Our bird comrades . nt to give the proper rebound and yet firmenough to support the birds weight. The longest quillsare those that grow on the hand or outer extremity of thewing and are known as the primaries. What are calledthe secondaries are attached to the ulna of the forearm,while the tertiaries occupy the humerus and are next tothe body. All these feathers are so placed relativelythat the stiff outer vane of each quill overlaps the moreflexible inner vane of its successor, like the leaves of certainkinds of fans, thus presenting an unbroken surface to theair. As to the structure of the
. Our bird comrades . nt to give the proper rebound and yet firmenough to support the birds weight. The longest quillsare those that grow on the hand or outer extremity of thewing and are known as the primaries. What are calledthe secondaries are attached to the ulna of the forearm,while the tertiaries occupy the humerus and are next tothe body. All these feathers are so placed relativelythat the stiff outer vane of each quill overlaps the moreflexible inner vane of its successor, like the leaves of certainkinds of fans, thus presenting an unbroken surface to theair. As to the structure of these plumes, they combinefirmness, lightness, and mobility, the barbs and barbulesknitting the more flexible parts together, so that they donot separate, but only expand, when the wing is the primary purpose of wings is flight, there isquite a number of notable exceptions. A concrete exam-ple is the ostrich, whose wings are too feeble to lift it fromthe ground, but evidently aid the great fowl in runnings. m CO ■^ T3 o Bird Flight 187 as it holds them outspread while it skims over the plain,perhaps using them mainly as outriggers or balancingpoles in its swift passage on its stilt-like legs. The penguinsconvert their wings into fins while swimming throughthe water, the feathers closely resembling scales. There are birds of many kinds, and therefore a greatvariety of wings and modes of flight. Birds with short,broad, roimded wings, with the under surface slightlyconcave and the upper surface correspondingly convex,usually have comparatively heavy bodies, and racethrough the air with rapid wing-beats and rather laboredfii^iit, and compass only short distances. Among the birdsof this kind of aerial movement may be mentioned theAmerican meadowlark, the bob-white, and the species propel themselves in rapid, gliding, andcontinued flight by means of long, narrow, and pointedwings, like the swifts, swallows, and goatsuckers, whilemany others, notably heron
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Keywords: ., bookcentury1900, bookdecade1900, bookidcu319240, booksubjectbirds
