or at least a large majority of them, have, in greater or lesser variety, cries and calls which are peculiar to certain seasons and certain situations; and since on many occasions we have indisputable evidence of the utility of the sound produced—as when, upon the alarm being given by one individual, the flock of Lapwing rises, or when, in response to a particular note of the parent, the nestling Blackcap ceases to call—so are we bound to infer that all the cries are, in one way or another, serviceable in furthering the life of the individual.
But besides these call-notes, birds produce special sounds during the season of reproduction—some by instrument, others by voice, others again by the aid of mechanical device. And not only is this the case, but many accompany their songs with peculiar flights, such as soaring to a great height, or circling, or floating in the air upon outstretched wings. These special sounds and special flights are those with which I now propose to deal including under the heading "song" all sounds whether harsh or monotonous or beautiful, and whether vocally or otherwise produced; and I shall endeavour to show not only that they are related to the "territory," but that they contribute not a little to the successful attainment of reproduction.
The vocal productions are infinite in variety and combination. At the one extreme we have songs composed of a single note repeated
