. The structure and life of birds . ich arepolygamous, and which consequently have an excessof males among whom there is constant war in spring-time. It is with his spur that the game-cock slayshis rival. The Beak. In the beak the horny covering which overlies thebone is a growth of the epidermis just as spurs are. 1 On moulting- see especially (i) Bronns Thier-Reichr vol. Aves, pp. 538-542 ; (2) Seebohms Brit. Birds, passim ; (3)Gatke, Die Vogclwarte Helgoland, pp. 156-166; (4) Le PigeonVoyageur, by F. Chapuis, pp. 103-111. I am indebted to M. Adamsons book Some more Scraps about Birds,
. The structure and life of birds . ich arepolygamous, and which consequently have an excessof males among whom there is constant war in spring-time. It is with his spur that the game-cock slayshis rival. The Beak. In the beak the horny covering which overlies thebone is a growth of the epidermis just as spurs are. 1 On moulting- see especially (i) Bronns Thier-Reichr vol. Aves, pp. 538-542 ; (2) Seebohms Brit. Birds, passim ; (3)Gatke, Die Vogclwarte Helgoland, pp. 156-166; (4) Le PigeonVoyageur, by F. Chapuis, pp. 103-111. I am indebted to M. Adamsons book Some more Scraps about Birds, printedfor private circulation M i62 THE STRUCTURE AND LIFE OF BIRDS char In all birds the upper beak moves slightly, in parrotsfreely. It is always growing, but constant frictionagainst hard substances and of the upper against thelower beak prevents this from being apparent. Theducks beak acts as a strainer: the whale, in the so-called whalebone, has a similar instrument which letsthe water pass away while retaining the food. The. Fig. 42.(1), Beak of Falcon showing toothed edge ; (2), of Duck showing strainer. beaks of Humming-birds are bent or otherwise shapedso as to suit the forms of particular flowers down thecorollas of which they dive for the honey. Falcons andother birds of prey have their upper beaks cut intoteeth, an assistance in tearing their food. And in con-nection with this, it must be remembered that flesh-eating birds have nothing worthy of the name of agizzard. Hence some tearing of the food is desirable. vi FORM AND, FUNCTION 163 Mr. Beddard mentions that the Great Spotted Wood-pecker ate the caterpillar of the Buff-tip moths partiallyafter much Was this because the conspicuouscolours frightened him or because the skin was over-tough ? A Magpie rubbed the hairs off a caterpillarbefore eating it. On the other hand a Gannet swallowsa mackerel whole. A Cormorant is only troubled by awhole fish if he happens to swallow him headforemostand so get the f
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