Thus geographical variability in the voice of insects and amphi- 

 bians is based on sharp fluctuations of both frequency and intensity. 

 Nemobius fas c iatus achieves the transmission of relevant information 

 by frequency variations in a spectrum of 200 to 1,000 cps (Pierce, 19A-8). 

 Sometimes the number of syllables (Jacob, 1957) or temporary peculiar- 

 ities of each syllable (Faber, 1953; Allard, 1957) indicates special 

 meanings. In the voice of amphibians frequency variations play an im- 

 portant role (Blair, 1955-58). Geographical information in the voice 

 of birds can be coded according to the same principles, though more 

 often than not it is coded by finer variations in the singing. 



Thus, the races of Parus atricapillus are distinguished by their 

 loud call, those of Zonotria . capensis by the rapidity of their rendi- 

 tion of certain elements of their song, and those of Emberzia or 

 Coturnix by the presence or absence of an introduction (Salomonsen, 

 1935; Chapman, 19^0; Borror, 1956). 



Quite often information is conveyed not by a special song but by 

 a particular aspect of its rendition. Thus Finnish and English night- 

 jars (Caprimulgus) sing at different times of day and night (Tembrock, 

 1959). 



The high level of development of the analyzer and of the higher 

 nervous activity in birds produces the following phenomenon: geograph- 

 ical voice variability in birds is as a rule related to the separate 

 parts of the spectrum. On the other hand the stridulation of insects 

 and the rather monotonous voices of amphibians vary throughout their 

 entire spectrum. All this has a definite biological significance. 



The functions of insect and amphibian voices, as compared to the 

 voices of birds, are considerably more restricted. In birds the voice 

 plays a part in all the principal phases of life: pairing, migration, 

 rearing of the young, defense against predators, etc., -which explains 

 the rich range of possibilities in birds' voices. Cariama cristata 

 alone possesses over 200 notes; Passeriformes, of course, have many 

 more notes at their disposal. Yet, although each of these notes can be 

 utilized for conveying several different signals, the possibilities of 

 coding them in that direction are not infinite. (A single note pro- 

 duced by passerines can have up to 15 connotations, depending on its 

 variations . ) 



In certain cases there arises the need for preserving the stabil- 

 ity of the "meaning" of a signal and of restricting its functional 

 load. In other cases the opposite is true, and a greater polyfunetion- 

 ality is required. 



Thus, for example, single phrases in the song of the chaffinch may 

 serve many purposes: delimitation of territory, identification of a 

 mate or a pair, danger signals, mating calls, nuptial display, flocking 

 signals and so on. (Marler, 1956). The element of geographical vari- 

 ability has very little effect on these functions, but can also be 



