08 December 2009

Vocal displays

No other group of vertebrates have developed auditory communication like birds: only primates are more complex. BIRD SONG IS THE DOMINANT NOISE IN FOREST.

Bird songs come from syrinx , which is found only in birds. It is located at the lower end of trachea and is analogous to our voice box. It is located where the bronchi come together but is not homologous to our voice box since there is no larynx and vocal chords. It works by syrngeal muscles surrounding junction and tympanic membranes on inner edges of bronchi. An extension of airsacs lies between tympanic membranes (see your text book). One result of this anatomy is that some songbirds can sing two songs at once!

After inhalation:
1) air sac fills with air between bronchi
2) tympanic membrane forced out all the way to other side of bronchus
3) pressure released from lungs
4) syrngeal muscles control how much air passes and vibrates tympanic membrane
5) syrngeal muscles exert a very fine control modulates vibration of membrane
6) the two tympanic membranes are independent in most passerines

Other sounds made by birds inlcude those from modified feather structures, like snipe tails and manakin wings.

Wilson's Snipe

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