Bird Songs and Mate Selection
Marler. P. 1960. Bird songs and mate selection. In: Lanyon, W.E. and Tavolga, W.N. eds. Animal Sounds and Communication, 7: 348–367. American Institute of Biological Sciences, Washington, DC.
Although bird songs have been the subject of much attention, particularly in recent years, there is hardly any direct information about how they actually function. In this respect bird studies are less advanced than, for example, those on Orthoptera (e.g. Perdeck 1957; Walker 1957), and there is no doubt that the greatest single need in studies of avian communication is for experiment in this field and in particular, on the value of songs as reproductive-isolating mechanisms. This subject must therefore be discussed at present in terms of indirect evidence, not all of which is as clear as is sometimes assumed.
Ornithologists are often impressed by the distinctiveness of the songs of species that live together. Often song is more useful for field identification than the morphology, and at least once has provided the first clue to the separation of new species (White 1879) (Fig. 1). This fact of specific distinctiveness in songs seems to carry the implication that they serve as reproductive-isolating mechanisms, either in establishing or perpetuating a bond between breeding birds, thus being subject to a selective pressure encouraging specific distinctiveness. Leaving aside for the moment the question whether specific distinctiveness of songs in sympatric species is in fact universal, we can make certain deductions about some of the characteristics that bird songs should have, when functioning in this way.