Utility of vocal formant spacing for monitoring sandhill crane subspecies

Jones, Matthew R.; Witt, Christopher C.

doi:10.1002/wsb.110

Cited by 4 publications

(1 citation statement)

References 22 publications

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“…Boeckle & Bugnyar () showed that ravens ( Corvus corax ) responded to calls of previously familiar and non‐affiliated individual by lowering the formant spacing and increasing the chaotic parts of the vocalisation in comparison with calls of an affiliated one, potentially exaggerating the perceived impression of body size. Moreover, formants can, at least in theory, provide acoustic cues to individuality and body size within the same bird's species, as previously demonstrated in mammals (Suthers ; Fitch ; Jones & Witt ).…”

Section: Introductionmentioning

confidence: 66%

Formant Frequencies are Acoustic Cues to Caller Discrimination and are a Weak Indicator of the Body Size of Corncrake Males

Budka

Osiejuk

2013

Ethology

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Source–filter theory assumes that calls are generated by a vocal source and are subsequently filtered by the vocal tract. The air in the vocal tract vibrates preferentially at certain resonant frequencies, called formants. Formant frequencies can be a good indicator of the caller's characteristics, such as sex, age, body size or individual identity. Although source–filter theory was originally proposed for mammals, formants are also observed in birds, and some bird species have been shown to perceive formants. In this study, we evaluated the hypotheses that formant frequencies (1) are an indicator of body size and (2) can be used for individual discrimination by a nocturnal bird species, the corncrake (Crex crex). We analysed calls of 104 males from Poland and the Czech Republic. Linear regression models showed that the males with a longer head (including the bill length) had a significantly lower formant dispersion and lower fourth and fifth formant frequencies. However, we found no significant relationships between body weight and any filter‐related acoustic measurement. The formant frequencies had smaller within‐ than between‐individual coefficients of variation. This characteristic of the formant frequencies implies a high potential for individual coding. A discriminant function analysis correctly assigned 94.8% of the calls to the caller based on formants from second to fifth. Our results indicated that the formant frequencies are a weak indicator of the body size of the sender in the corncrake. However, even weak dependence between body size and acoustic properties of signal may be important in natural selection process. Alternatively, such a weak dependence may be observed, because receivers ignore the acoustical, formant‐based cues of body size. Simultaneously, the formants might potentially provide acoustic cues to individual discrimination and could be used to census and monitoring tasks.

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Section: Introductionmentioning

confidence: 66%

Formant Frequencies are Acoustic Cues to Caller Discrimination and are a Weak Indicator of the Body Size of Corncrake Males

Budka

Osiejuk

2013

Ethology

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Sound and Vocal Production and Function

Ritchison

2023

Fascinating Life Sciences

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Migrate small, sound big: functional constraints on body size promote tracheal elongation in cranes

Jones

Witt

2014

J of Evolutionary Biology

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Organismal traits often represent the outcome of opposing selection pressures. Although social or sexual selection can cause the evolution of traits that constrain function or survival (e.g. ornamental feathers), it is unclear how the strength and direction of selection respond to ecological shifts that increase the severity of the constraint. For example, reduced body size might evolve by natural selection to enhance flight performance in migratory birds, but social or sexual selection favouring large body size may provide a countervailing force. Tracheal elongation is a potential outcome of these opposing pressures because it allows birds to convey an auditory signal of exaggerated body size. We predicted that the evolution of migration in cranes has coincided with a reduction in body size and a concomitant intensification of social or sexual selection for apparent large body size via tracheal elongation. We used a phylogenetic comparative approach to examine the relationships among migration distance, body mass and trachea length in cranes. As predicted, we found that migration distance correlated negatively with body size and positively with proportional trachea length. This result was consistent with our hypothesis that evolutionary reductions in body size led to intensified selection for trachea length. The most likely ultimate causes of intensified positive selection on trachea length are the direct benefits of conveying a large body size in intraspecific contests for mates and territories. We conclude that the strength of social or sexual selection on crane body size is linked to the degree of functional constraint.

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Utility of vocal formant spacing for monitoring sandhill crane subspecies

Cited by 4 publications

References 22 publications

Formant Frequencies are Acoustic Cues to Caller Discrimination and are a Weak Indicator of the Body Size of Corncrake Males

Formant Frequencies are Acoustic Cues to Caller Discrimination and are a Weak Indicator of the Body Size of Corncrake Males

Sound and Vocal Production and Function

Migrate small, sound big: functional constraints on body size promote tracheal elongation in cranes

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