. The bird, its form and function . r residents to cease their roving,they prepare to develop all the advantages which mayin any way aid them in securing a mate. Some indus-triously practise dance-steps, others flight-evolutions, alarger number rehearse their songs under their breath,while still others passivels await the development ofplumes, gorgets, spots and splashes of colour w^hich, ifthe feathers come out large and brilliant, may stand themin as good stead in their wooing as any song or we find a class of birds which have a partial or com-plete moult in the spring. These feat
. The bird, its form and function . r residents to cease their roving,they prepare to develop all the advantages which mayin any way aid them in securing a mate. Some indus-triously practise dance-steps, others flight-evolutions, alarger number rehearse their songs under their breath,while still others passivels await the development ofplumes, gorgets, spots and splashes of colour w^hich, ifthe feathers come out large and brilliant, may stand themin as good stead in their wooing as any song or we find a class of birds which have a partial or com-plete moult in the spring. These feathers may last ail 46 The Bird summer, or may drop out as soon as begins the hardwork of building the nest or feeding the young, with whichlabor they might interfere. To return for a moment to the fall moult. If a spar-row or lark should shed all of its large wing-featherssimultaneously, it would have slight hope of ever livinglong enough for new ones to grow out again. If suchdefenceless birds were compelled to hop helplessly along. Fig. 2S.—Wings of Sparrow, showing two feathers of each wing being moulted simultaneously. the ground, weasels and cats would be able to catchhundreds of them without effort. This is avoided in allland birds by the moulting of only a pair of primaries,as the large flight-feathers are called, at a time, one fromeach wing. This process usually starts with the pairfarthest from the front of the wing, and the second pairdoes not fall out until the first pair of new feathers isnearly of full size. Thus all danger of a crippled flightis avoided. One of the most interesting phases of Nature is theway she provides for exceptions to what we are pleasedto call her laws. Some birds, unlike those mentioned Feathers 47 above, shed every primary in their wings at once, so thattheir angular stump-feathered wings are perfectly uselessfor flight. In this class are many water birds—ducks,geese, flamingoes, snake-birds and others. Just before thiswholesal
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