bird call

Bird songs are certain vocal sounds that birds make—in non-technical use, those sounds that are melodious to the human ear. In ornithology, bird 'songs' are often distinguished from shorter sounds, which may be termed 'calls'.

Definition

The distinction between songs and calls is somewhat arbitrary. Ehrlich et al. say that songs are longer and more complex, and that calls tend to serve such functions as alarms or keeping members of a flock in contact, while songs claim territory and advertise for mates. Other authorities such as Howell (1994) make the distinction based on function, so that even short vocalisations such as those of pigeons are considered songs—and even non-vocal sounds such as the drumming of woodpeckers and the "winnowing" that snipes' wings make in display flight. Still other investigators say that song must have syllabic diversity and temporal regularity akin to the repetitive and transformative patterns which define music.

Bird song is best developed in the order Passeriformes. Most song is emitted by male rather than female birds.

Anatomy

The avian vocal organ is called the syrinx; it is a bony structure at the bottom of the trachea (unlike the larynx at the top of the mammalian trachea). The syrinx and sometimes a surrounding air sac resonate to vibrations that are made by membranes past which the bird forces air. It controls the pitch by changing the tension on the membranes and controls both pitch and volume by changing the force of exhalation.The bird can control the two sides of the trachea independently, which is how some species can produce two notes at once.

Learning

The songs of different species of birds vary, and are more or less characteristic of the species. In modern-day biology, bird song is typically analysed using acoustic spectroscopy. Species vary greatly in the complexity of their songs and in the number of distinct kinds of song they sing (up to 3000 in the Brown Thrasher); in some species, individuals vary in the same way. In a few species such as starlings and mockingbirds, songs imbed arbitrary elements learned in the individual's lifetime, a form of mimicry (though maybe better called "appropriation" [Ehrlich et al.], as the bird doesn't pass for another species). In many species it appears that although the basic song is the same for all members of the species, young birds learn the details of their songs from their fathers, and this allows variations to build up over generations, a form of dialect.

Birds learn songs early in life with subvocalizations that develop into renditions of adult songs. Zebra Finches, the most popular specimen used in birdsong research, develop a version of a familiar adult's song after 20 or more days from hatch. By around 35 days, the chick will have learned the adult song. By around 60 days rehearsal has perfected the song which after another 30 days, at sexual maturity, becomes invariant.

Research indicates bird song is a form of motor learning that involves regions of the basal ganglia. Models of bird song motor learning are sometimes used as a model for how humans learn speech, and indeed they share many similarities, such as requiring teachers, practice, error-correction, and eventually becoming more difficult to learn after the bird or human reaches sexual maturity.

Researchers suggest birds learn songs, rather than inherit their sounds genetically. Research has hypothesized learned songs allow the development of more complex songs through cultural interaction, it allows intraspecies dialects that help birds stay with their own kind within a species, and it allows birds to adapt their songs to different acoustic environments. (Slater, 1989)

Neurology of song production and learning

Birdsong learning occurs along neural pathways that connect the hyperstriatum ventralis, which is a region unique to the avian pallium, to the robust nucleus of the archistriatum. The pathway traverses the paraolfactory lobe, the dorso-lateral division of the medial thalamus, and the lateral magnocellular nucleus of the anterior neostriatum. (The neostriatum is similar to the putamen in the basal ganglia of mammals.) Cells in along the learning pathway accumulate testosterone, suggesting androgens might be involved in birdsong learning.

Birdsong production is generally thought to start at the nucleus uvaeformis of the thalamus with signals emanating along a pathway that terminates at the syrinx. The pathway from the thalamus leads to the interfacial nucleus of the neostriatum, high vocal center, which is the hyperstriatum ventralis, then to the robust nucleus of the archistriatum, the dorso-lateral division of the medial thalamus and to the tracheosyringeal nerve.

Disruptions along the learning pathway between 20 and 60 days of a finch's life permanently damages the bird's song, but has no effect if the same pathways were disrupted later in life. Disruptions along the production pathways can always damage a birds ability to sing.

Recent research in birdsong learning has focused on the area ventralis of Tsai, which produces dopamine to the paraolfactory lobe, the lateral magnocellular nucleus of the anterior neostriatum and the ventrolateral medulla. Other researchers have explored the possibility that the high vocal center is responsible for syllable production, while the robust nucleus of the archistriatum, the primary song output nucleus, may be responsible for syllable sequencing and production of notes within a syllable.

Language

The language of the birds has long been a topic for anecdote and speculation. Certain meanings, such as those of different types of calls by hens, have been taken as a matter of course [1]. Modern science has just begun to investigate this type of animal language. Researchers have described up to twenty-two different types of crow calls made under varying circumstances. In a 2005 study by Chris Templeton et al. published in the journal Science, it was shown that the number of "dees" in a chick-a-dee call corresponds to the degree of danger that a predator poses (See Why Files overview).

Interestingly, the gene FOXP2, defects of which affect both speech and comprehension of language in humans, becomes more active in the striatal region of songbirds during the time of song learning [2].

Human culture

Bird song is often imitated in music, especially song or whistling. Several classical composers have incorporated it into their music. Ludwig van Beethoven, for example, included imitations of the Nightingale, Common Quail and Common Cuckoo in his Symphony No. 6 (the Pastoral). The French composer Olivier Messiaen had a particular interest in bird song, carefully notating many birds' cries and incorporating them into his music (his Catalogue d'oiseaux for solo piano is especially notable in this regard).

François-Bernard Mâche's Musique, mythe, nature, ou les Dauphins d'Arion (1983), includes a study of "ornitho-musicology" using a technique of Nicolas Ruwet's Language, musique, poésie (1972) paradigmatic segmentation analysis, shows that bird songs are organized according to a repetition-transformation principle used to analyze human music.

Recorded bird songs have also been used, as Ottorino Respighi was the first to do, in The Pines of Rome. In the psychedelic 60's and 70's era, many bands included sound effects in their songs. Bird songs were among the most-used effects. Especially the band Pink Floyd liked them. They can be heard in many songs from Pink Floyd's 1969 albums More and Ummagumma (for example in the song Cirrus Minor).

Bird song is also a popular subject in poetry. Famous poems inspired by bird song include Shelley's To a Skylark ("Hail to thee, blithe Spirit!/Bird thou never wert") and Gerard Manley Hopkins' Sea and Skylark.

Transcriptions of bird songs

Many people have used words or nonsense syllables to represent bird vocalizations. Naturally these 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 writers of bird guides interpret as "Who cooks for you? Who cooks for you all?" (Sibley 2000) with the emphasis placed on "you."

Nevertheless, some order may be found by referring to the scale of vowels. Low-frequency (back) vowels such as "oo" and "oh" usually represent low pitches, while high-frequency (front) vowels such as "ee" represent high pitches. The "w" sound is a glide from "oo" to a higher frequency, so a transcription such as tweet usually represents a rising pitch. Likewise the "y" sound is a glide from "ee" to a lower frequency, so yoo or tew usually represents a falling pitch. Transcriptions such as eer and ir also usually represent falling pitch, as does ow. Among consonants, s often represents an extremely high pitch and l a low pitch.

For example, we could expect the call of the Whip-poor-will to be an upward glide that ends abruptly, followed by a low note, followed by one that glides upward and then back down. This is precisely what careful listening (as to the Real Audio file at this page) or sonic analysis shows.

This method generally works only for whistles. Lower-pitched coos and squawks give the impression of vowels from their overtones, so the vowel gives little or no information about the fundamental frequency. Also, people's perceptions still vary greatly, even more if they speak different native languages, so one can't understand transcriptions with perfect reliability.

See also

• Language of the birds
• Animal communication
• Animal language
• Bioacoustics

References

• Bottjer SW, Miesner EA, Arnold AP (1984).
• Konishi, M. (1989). Birdsong for Neurobiologists.
• Yu and Margoliash (1996).
• Templeton et al. (2005).
• Howell, Steve N. G., and Sophie Webb (1994). A Guide to the Birds of Mexico and Northern Central America. Oxford University Press. ISBN 0-1985-4012-4.
• Ehrlich, Paul R., David S. Dobkin, and Darryl Wheye. "Bird Voices" and "Vocal Development" from Birds of Stanford essays
• Robbins, Chandler S., Bertel Bruun, Herbert S. Zim, Arthur Singer (2001). Birds of North America : A Guide To Field Identification. Golden Guides from St. Martin's Press. ISBN 1-58238-090-2. Gives sonograms for most species.
• Sibley, David (2000). The Sibley Guide to Birds. Knopf. ISBN 0-679-45122-6.

External links

• Large collection of audio bird calls
• Community database of bird song recordings from Central and South America 6666 recordings of 2261 species as of September 12, 2006.
• Archive of 150,000 recordings of over 8,000 bird species.
• Listen to Nature includes article "The Language of Birds"