How birds sing and why it matters 273 Chapter 9 Variation in Syringeal Structure Tracheal syrinx , Bronchial syrinx Tracheobronchial syrinx I (Parrot) (Oilbird) (Canary) I I How birds sing and why it matters RODERICK A. SUTHERS 'I 1 I! ! I MT INTRODUCTION briefly to indicate the variety of avian vocal I systems, and to provide a perspective from which I 1 I Songbirds have both an esthetic and a scientific to focus on the oscine songbirds. Readers 1 impact on our lives. Birdsong adds beauty and interested in additional information on songbirds Figure 9.1 Examples of variation in syringeal anatomy. The tracheal parrot syrinx has two syringeal vitality to our environment, The possibility of should consult reviews of this subject (Nowicki muscles and a pair of lateral tympaniform membranes. The bronchial syrinx of the oilbird has one pair of its absence due to increasing levels of & Marler 1988; Suthers 1997, 1999a, b; Gaunt syringeal muscles and a pair of medial and lateral tympaniform membranes in each bronchus. Songbirds environmental toxins, so eloquently described & Nowicki 1998; Doupe 81 Kuhl 1999; Suthers have several pairs of syringeal muscles in their tracheobronchial syrinx. Tr, trachea; ST, sternotrachealis by Rachel Carson (1962) in her goundbreaking ef ale 1999; Goller & Larsen 2002)- muscle; SY SUP, superficial syringeal muscle; SY PROF, deep syringeal muscle; SY VALV, pneumatic valve; LTM, lateral tympaniform me~brane;MTM, medial tympaniform membrane; BCI, first bronchial book, Silent Spring, was a potent factor in cartilage; SY, syringeal muscle; ML, medial labium; LL, lateral labium; SYR, muscles of syrinx. (Oilbird mobilizing public opinion to become better modified after Suthers & Hector 1985; parrot and canary modified after King 1989). stewards of our environment. Scientifically, the highly developed vocal communication of this AN ORGAN FOR SINGING The Respiratory Rhythm group, sharing as it does a number of parallels direction through the syrinx and into the with speech, has made songbirds especially suited The avian vocal organ, the syrinx, is located The timing of vocalization and the tempo of esophagus. After each coo there is a short for the study of complex, learned vocal deep in the chest in an air sac that is connected song begins with the respiratory cycle (Vicario expiration followed by a brief inspiration (Gaunt communication at every level, from its molecular to other air sacs and the lungs. It is present in all 1 991). Expiratory muscles compress the bellows- et al. 1982). biology to its evolution. birds except vultures, but its exact location and like air sacs in the thorax and abdomen, increasing This chapter is about how birdsong is structure varies considerably (King 1989). In respiratory pressure so air flows out through the produced. How do birds generate such a variety some species, including doves, pigeons and syrinx and trachea (Hartley 1990). During song, The Source of Sound of sounds and what vocal gymnastics are required parrots, the syrinx consists of modified rings of a small inspiration called a 'mini-breath' (Calder It is now generally agreed that vocalizations are to produce them?The vocal system is the interface cartilage near the lower end of trachea 1970) is usually taken after each syllable, except generated by airflow-induced oscillation of between the bird's brain and his song. Knowing (Fig. 9.1). at very high syllable repetition rates (Hartley & elements in the wall of the syrinx that convert how it functions, and coming to appreciate its In other species, such as penguins, many owls, Suthers 1989). Inspiratory muscles expand the some of the air's kinetic energy into acoustic limitations as well as its capabilities, is important nightjars, and some cuckoos, the syrinx thorax and abdomen, reducing pressure in the energy. These oscillations are presumably in understanding vocal communication. Birdsong exists as two semisyrinxes located in the primary air sacs and reversing the direction of airflow sustained by interaction between Bernoulli forces is the product of the carefully coordinated activity bronchi (Fig. 9.1). In many birds, however, through the syrinx (Wild et al. 1998). and the inertia of air in the vocal tract, in much of many different muscles. Some of these are including but by no means limited to the oscine Vocalization occurs during expiratory airflow, the same way as are oscillations of human vocal associated with the vocal organ but many belong songbirds, the syrinx is at the junction where aside from rare exceptions when it occurs during folds (Titze 1994; Gardner et al. 200 1). An to other muscle groups such as the respiratory the two primary bronchi join to form the trachea. inspiration, as in the 'wah' sounds of doves (Gaunt alternative mechanism for sound production system and the vocal tract. Together they convert This tracheobronchial syrinx includes modified I et al. 1982), and certain syllables in the songs of based on the principle of an aerodynamic whistle nerve impulses from the brain into song. cartilages from both the upper end of each some zebra finches (Goller & Daley 2001). Most was put forth (Gaunt et al. 1982) to explain Less is known about the vocal mechanisms of bronchus and the lower end of the trachea birds sing with their beaks open, but doves and pure tone vocalizations in birds such as doves. non-songbirds, and they will be mentioned only (Fig. 9.1). pigeons coo with their beaks and nares closed. However, this aerodynamic whistle hypothesis Sound is produced during airflow in an expiratory is not supported by the observation of How birds sing and why it matters 273 Chapter 9 Variation in Syringeal Structure Tracheal syrinx , Bronchial syrinx Tracheobronchial syrinx I (Parrot) (Oilbird) (Canary) I I How birds sing and why it matters RODERICK A. SUTHERS 'I 1 I! ! I MT INTRODUCTION briefly to indicate the variety of avian vocal I systems, and to provide a perspective from which I 1 I Songbirds have both an esthetic and a scientific to focus on the oscine songbirds. Readers 1 impact on our lives. Birdsong adds beauty and interested in additional information on songbirds Figure 9.1 Examples of variation in syringeal anatomy. The tracheal parrot syrinx has two syringeal vitality to our environment, The possibility of should consult reviews of this subject (Nowicki muscles and a pair of lateral tympaniform membranes. The bronchial syrinx of the oilbird has one pair of its absence due to increasing levels of & Marler 1988; Suthers 1997, 1999a, b; Gaunt syringeal muscles and a pair of medial and lateral tympaniform membranes in each bronchus. Songbirds environmental toxins, so eloquently described & Nowicki 1998; Doupe 81 Kuhl 1999; Suthers have several pairs of syringeal muscles in their tracheobronchial syrinx. Tr, trachea; ST, sternotrachealis by Rachel Carson (1962) in her goundbreaking ef ale 1999; Goller & Larsen 2002)- muscle; SY SUP, superficial syringeal muscle; SY PROF, deep syringeal muscle; SY VALV, pneumatic valve; LTM, lateral tympaniform me~brane;MTM, medial tympaniform membrane; BCI, first bronchial book, Silent Spring, was a potent factor in cartilage; SY, syringeal muscle; ML, medial labium; LL, lateral labium; SYR, muscles of syrinx. (Oilbird mobilizing public opinion to become better modified after Suthers & Hector 1985; parrot and canary modified after King 1989). stewards of our environment. Scientifically, the highly developed vocal communication of this AN ORGAN FOR SINGING The Respiratory Rhythm group, sharing as it does a number of parallels direction through the syrinx and into the with speech, has made songbirds especially suited The avian vocal organ, the syrinx, is located The timing of vocalization and the tempo of esophagus. After each coo there is a short for the study of complex, learned vocal deep in the chest in an air sac that is connected song begins with the respiratory cycle (Vicario expiration followed by a brief inspiration (Gaunt communication at every level, from its molecular to other air sacs and the lungs. It is present in all 1 991). Expiratory muscles compress the bellows- et al. 1982). biology to its evolution. birds except vultures, but its exact location and like air sacs in the thorax and abdomen, increasing This chapter is about how birdsong is structure varies considerably (King 1989). In respiratory pressure so air flows out through the produced. How do birds generate such a variety some species, including doves, pigeons and syrinx and trachea (Hartley 1990). During song, The Source of Sound of sounds and what vocal gymnastics are required parrots, the syrinx consists of modified rings of a small inspiration called a 'mini-breath' (Calder It is now generally agreed that vocalizations are to produce them?The vocal system is the interface cartilage near the lower end of trachea 1970) is usually taken after each syllable, except generated by airflow-induced oscillation of between the bird's brain and his song. Knowing (Fig. 9.1). at very high syllable repetition rates (Hartley & elements in the wall of the syrinx that convert how it functions, and coming to appreciate its In other species, such as penguins, many owls, Suthers 1989). Inspiratory muscles expand the some of the air's kinetic energy into acoustic limitations as well as its capabilities, is important nightjars, and some cuckoos, the syrinx thorax and abdomen, reducing pressure in the energy. These oscillations are presumably in understanding vocal communication. Birdsong exists as two semisyrinxes located in the primary air sacs and reversing the direction of airflow sustained by interaction between Bernoulli forces is the product of the carefully coordinated activity bronchi (Fig. 9.1). In many birds, however, through the syrinx (Wild et al. 1998). and the inertia of air in the vocal tract, in much of many different muscles. Some of these are including but by no means limited to the oscine Vocalization occurs during expiratory airflow, the same way as are oscillations of human vocal associated with the vocal organ but many belong songbirds, the syrinx is at the junction where aside from rare exceptions when it occurs during folds (Titze 1994; Gardner et al.