. Bird-life : a guide to the study of our common birds . water, it wouldnot be obliged to rise into the air, and, as a result of dis-use, the wings would finally become too small to support itin aerial flight, though fully answering the purpose of oars. Apparently this is what has happened in the case ofthe Razor-billed Auks relative, the flightless, extinctGreat Auk. The Razor-bill is sixteen inches long andits wing measures eight inches, while the Great Auk,with a length of thirty inches, has a wing only five andthree fourths inches in length. Aside from this differ-ence in measurements thes
. Bird-life : a guide to the study of our common birds . water, it wouldnot be obliged to rise into the air, and, as a result of dis-use, the wings would finally become too small to support itin aerial flight, though fully answering the purpose of oars. Apparently this is what has happened in the case ofthe Razor-billed Auks relative, the flightless, extinctGreat Auk. The Razor-bill is sixteen inches long andits wing measures eight inches, while the Great Auk,with a length of thirty inches, has a wing only five andthree fourths inches in length. Aside from this differ-ence in measurements these birds closely resemble eachother. So far as we are familiar with the Great Aukshabits, they agreed with those of the hypothetical case Ihave ]ust mentioned, and we are warranted, I think, inassuming that the bird lost the power of flighc throughdisuse of its wings. FORM AND HABIT: THE WING. 21 In antarctic seas we find the arctic Auks replacedby the Penguins, a group in wliicli all the members areflightless. Thej are possessed of i-emarkahle Fig. 8.—Great Auk, showinrr relatively Pimill wincfinches; of wing, 5 75 inches.) (Length of bird, 3G powers, and can, it is said, outswira even fish. Theynest only on isolated islands, where they are not exposedto the attack of predaceous mammals. Among Grehes and Ducks we have illustrations ofthe way in which swimming birds may become tempo-rarily flightless. With most land-inhabiting birds flightis so important a faculty that any injury to the wings isapt to result fatally. It is necessary, therefore, thatthe power of flight shall not be impaired. Conse-quently, when molting, the wing-feathers are shedslowly and symmetrically, from the middle of the wingboth inwardly and outwardly; the new feathers ap-pear so at no time are there more thantwo or three quills missing from either wing. But the 22 FORM AND HABIT: THE WING. aquatic Grebes and Ducks, protected by the nature oftheir haunts and habits, lose all their
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