Bird Vocalization - Identification and Systematics

Identification and Systematics

The specificity of bird calls has been used extensively for species identification. The calls of birds have been described using words or nonsense syllables or line diagrams. Common terms in English include words such as quack, chirp and chirrup. These are subject to imagination and vary greatly; a well-known example is the White-throated Sparrow's song, given in Canada as O sweet Canada Canada Canada and in New England as Old Sam Peabody Peabody Peabody (also Where are you Frederick Frederick Frederick?). In addition to nonsense words, grammatically correct phrases have been constructed as likenesses of the vocalizations of birds. For example, the Barred Owl produces a motif which some bird guides describe as Who cooks for you? Who cooks for you all? with the emphasis placed on you.

The use of spectrograms to visualize bird song was first introduced by W. H. Thorpe. These visual representations are also called sonograms or sonagrams. Some recent field guides for birds use sonograms to document the calls and songs of birds. The sonogram is objective, unlike descriptive phrases, but proper interpretation requires experience. Sonograms can also be roughly converted back into sound.

Bird song is an integral part of bird courtship and is a pre-zygotic isolation mechanism involved in the process of speciation. Many allopatric sub-species show differences in calls. These differences are sometimes minute, often detectable only in the sonograms. Song differences in addition to other taxonomic attributes have been used in the identification of new species. The use of calls has led to proposals for splitting of species complexes such as those of the Mirafra bushlarks.