Lecture 7.pdf

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Ecology & Evolutionary Biology
Michael Denny

Lecture 7 Bird Song IntroductionEuropean starlingsong consists of a complex mix of rattles gurgles whistles and buzzess It has been more nicely described as an excellent rendering of water gurgling from a tap sometimes ending with a couple of harsh rasping notes they are excellent mimics they are vocal learnersother wellstudied mimics are the Mockingbird Mimus polyglottos and the Superb Lyrebird Menura novaehollandiae of Australia o The common factor in these species is that they copy sounds that are not speciesspecific they will learn songs from other species including humanso And they can learn new songs throughout life Another wellknown example of mimicry does not involve songSome parrots can imitate human speech very wellHow Birds Communicate with SoundsBirds make a variety of sounds for communicationIn addition to songs and calls species of hummingbirds manakins and woodcocks vibrate individual wing feathers to create buzzy noises typically during courtship displayMale Ruffed Grouse in the dense northern forests produce drumming sounds by rapid wing movements while they are perched near the groundMale sage grouse produce popping sounds when they expel air from oesophageal air sacs in their elaborate courtshipStorks which do not make vocalizations clatter their bill together insteadPigeons will clap their wings together in flightWoodpeckers will pound their beak against a hollow tree trunk hydro pole or even metal guttering to create a drumming soundSkilled bird watchers can distinguish the drumming sounds of downy and hairy woodpeckersIn a novel form of drumming Palm Cockatoos Probosciger aterrimus from Australasia fashion a drumstick tool from a branch and then beat it against a hollow trunk during courtshipSongs and CallsSong and calls are produced initially from the syrinx and the sounds are modulated by the trachea throat tongue and beakBoth songs and calls function in communication but they differ in a number of waysSongs are usually long and complex compared to calls but the songs of some birds such as the house sparrow consist of short cheepsSongs are learned calls are innateSongs are usually produced by males in the breeding season and are functionally related to courtshipBut some birds sing yearround although song intensity increases in breeding season and in many species females sing eg whitecrowned sparrows northern cardinalSinging usually has a diurnal rhythm occurring primarily in the early morning dawn chorus and at duskCalls are diverse and used in a variety of survival and feeding contexts including alarm contact and flightBut there are also calls used in courtship eg precopulatory callsSong StructureThe study of bird song was advanced with the invention of the spectrograph or sonogram o It enables the user to graph sound in a frequencytime plot o The waveform or oscillogram the default graph in AUDACITY shows power or amplitude loudness vs time o The sonogram plots frequency pitch versus timeo Frequency is cyclessecond usually measured in Hertz and it is the inverse of wavelength smaller wavelength higher frequencyAlthough bird songs are complex melodies at the individual level they can be broken down into a hierachical structureo Notes elementscontinuous sound trace
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