bird song

Why bird song?Search answers? Sve o grdelinima

Lokacija: Primorski Dolac, Croatia

grdelini-sve o grdelinima

srijeda, 8. listopada 2008.

Researchers who study birds know that the quality of the birdsong is a good indicator of fitness. Evolutionary biologist Marlene Zuk, writing in the entertaining Riddled With Life: Friendly Worms, Ladybug Sex, and the Parasites That Make Us Who We Are, describes how disease and parasites drive the evolution of showy colors, structures and behavior. She and a colleague theorized that female birds use these features to select males who are more parasite-free, and thus species with more parasites should have evolved flashier colors and songs to distinguish the fittest males.

Indeed, their research showed that brighter bird species had more parasites, as did those that sang more musically complex songs. In another study, researchers discovered that the type of immunity exerted an influence on birdsong: the number of song bouts was higher in birds with better cell-mediated immunity (general immunity that aids wound healing) and the length of the bouts greater in birds with better humoral (i.e., antibody) immunity.

In addition to the role of birdsong in the mating ritual, many birds have unique songs that they sing under special circumstances: flight, aggression, dawn, nightfall. Recently, while walking in a park at dusk, I heard emanating from one dense tree an almost deafening cacophony like a hundred teenagers on the phone. As I passed close to the avian highrise, the twittering abruptly stopped: "Shh! My parents are listening." Once I'd passed underneath, it started up again. Some researchers theorize that these peak activities at dusk and dawn occur because acoustic factors make these the best times for sound transmission over distance.

Birds use calls to warn other birds of predators. Domestic chickens have distinct alarm calls for aerial and ground predators, a practice observed in some mammalian species as well. Individual birds also seem to be able to identify each other through their calls: mothers and chicks, mates, members of a flock.

Many birds engage in duet calls, where the male's call is answered antiphonally by the female in a call and response, but the significance of this is unclear. Some birds, such as starlings and mockingbirds, creatively incorporate arbitrary musical bits learned during the individual's lifetime. In many species, although the basic song is the same for all members of the species, young birds learn some details of their songs from their fathers, which get passed down through generations.

Composers have long been interested in representing birdsong in music. One of the earliest surviving pieces is the 13th century "Sumer is icumen in," which imitates the cuckoo. Beethoven and Mahler each imitated birdsong in a symphony, as did Bartok in the third piano concerto. Birdsong features prominently in the music of 20th century composer Olivier Messiaen. Jazz clarinetist David Rothenberg has written an informative book, Why Birds Sing: A Journey Into the Mystery of Bird Song, and recorded a CD of music based on the sounds of birds.

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