Next in importance to dancing and movement in the aid of courtship among birds is their use of song and display of decorative plumage. With them it would seem, even more than among the mammals or with man, sexual desire raises and intensifies all the faculties, and lifts the individual above the normal level of life. The act of singing is a pleasurable one, an expression of superabundant energy and joyous excitement. Thus love-songs, serving first probably as a call of recognition from the male to the female, came to be used as a means of seduction. Every one is familiar with the exquisite lyrical tournaments of our nightingales; their songs during the love season do not cease by day or by night, so that one wonders when sleep can be taken; but as soon as the young are hatched the music ceases, and harsh croaks are the only sound left.[70] The song of the skylark, with its splendid note of freedom, is more melodious and more frequent in the season of love's delirium.[71] Another bird, the male of the weaver bird, builds an abode of pleasure for himself, wherein he retires to sing to his mate.[72] A very beautiful case of the use of these love-calls by the tyrant bird (_Pitangus Bolivianus_) is recorded by W.H. Hudson.[73] "Though the male and female are greatly attached they do not go afield to hunt in company, but separate to meet at intervals during the day. One of the couple (say the female) returns to the trees where they are accustomed to meet, and after a time becoming impatient or anxious at the delay of her consort, utters a very long, clear call-note. He is perhaps a quarter of a mile away, watching for a frog beside a pool, or beating over a thistle bed, but he hears the note and presently responds with one of equal power. Then, perhaps, for half-an-hour, at intervals of half-a-minute, the birds answer each other, though the powerful call of the one must interfere with his hunting. At length he returns: then the two birds, perched close together, with their yellow bosoms almost touching, crests elevated, and beating the branch with their wings scream their loudest notes in concert--a confused, jubilant noise that rings through the whole plantation. Their joy at meeting is patent, and their action corresponds to the warm embrace of a loving human couple." Some birds, who are ill-endowed from a musical point of view, have their wing feathers or tails peculiarly developed and stiffened, and are able to produce with them a strange snapping or cracking sound. Thus several species of snipe make drumming or "bleating" noises--something like the bleat of a goat--with their narrowed tails as they descend in flight.[74] Magpies have a still more curious method of call, by rapping on dry and sonorous branches, which they use not only to attract the female, but also to charm her. We may say that these birds perform instrumental music.[75]