VOICE OF BIRDS. 63 is a most welcome promise of spring. Then follow the Robins, Blackbirds, and other migrants, until, late in May, the great springtime chorus is at its height. The Bobolink is the first bird to desert the choir. We do not often hear him after July 5. Soon he is fol- lowed by the Yeery, and each day now shows some fresh vacancy in the ranks of the feathered singers, until by August 5 we have left only the Wood Pewee, Indigo Bunting, and Red-eyed Vireo — tireless songsters who fear neither midsummer nor midday heat. Call-Notes. — The call-notes of birds are even more worthy of our attention than are their songs. Song is the outburst of a special emotion ; call-notes form the language of every day. Many of us are familiar with birds' songs, but who knows their every call-note and who can tell us what each call means ? For they have a meaning that close observation often makes intelligible. Listen to the calls of the Robin and learn how unmis- takably he expresses suspicion, alarm, or extreme fear ; how he signals cheerfully to his companions or gives the word to take wing. Study the calls of the Crow or Blue Jay, and you will find that they have an apparently ex- haustless vocabulary. It is supposed that birds, like men, do not mherit their language, but acquire it. Thus there are recorded instances of young birds who had been isolated from others of their kind, learning to sing whatever song they heard. On the other hand, it is said that a bird inherits its own notes, at least to some extent, and, while it may not sing the song of its species perfectly, its song will still be sufficiently characteristic to be recognizable. There are, however, very few satisfactory observations on this subject, and keepers of cage-birds have here an excellent opportunity for original investigation.
