Introduction

The Piha (Lipaugus vociferans) is a bird that populates many of the South American forests. It is known as the Screaming Piha because it can produce an incredibly loud call that sounds to humans like a high-pitched scream. The bird has a dark gray color and is perched on the higher branches of trees in the forest. Its mass is about 68–87 grams, and its length is about 25 cm beak to tail (Suzuki, et al., 2020). Its famous scream is called the “qui-qui-yo” (Nemeth, 2004). Prior to the scream, it usually produces a preliminary “groo” sound with the head in normal position and the beak only slightly open (Figure 1, left). This pre-scream “groo” might set the larynx for the scream and could resemble a semi-occluded vocal tract (SOVT) gesture. The following syllables, the “qui-qui,” are performed with the head cocked backwards, deeply embedded in a round inflated body, with the beak wide open (Figure 1, right). The call ends with the “yo”, where the head and beak are extended forward.

Figure 2 depicts a side view of the Piha’s neck retraction during the “qui” sound (left), followed by the neck extension during the “yo” (right).

The Piha diet consists of fruit and insects. It is estimated that the bird burns on the order of 25 kcal a day based on food intake (Lasiewski & Dawson, 1967). It is known to forage in the canopy, often swallowing fruit whole, and maintains a high-energy diet to support long, uninterrupted periods of calling.

Acoustic power versus caloric intake

Consider the acoustic energy radiated in vocalization as a fraction of daily caloric energy intake. In humans, the caloric intake is ≈ 2000 kcal, or 8.37 million Joules (MJ). This energy supplies the power to contract respiratory and phonatory muscles for vocalization. It also produces the aerodynamic power in the glottis and the power needed to oscillate the vocal folds. A fraction of the aerodynamic power is converted to acoustic power, and a fraction of that power is radiated to the listener. Most of the acoustic and aerodynamic powers are absorbed in the vocal tract.

It has been shown that in humans the acoustic power radiated from the mouth in speech is on the order of 0.01–1.0 milliwatt (mW), as reported by Schutte (1980). In loud shouting or singing it can be on the order of 1.0 Watt (W) (Bouhuys et al., 1968). Let’s assume a human can shout or sing loud notes for an accumulated phonation time of 2 hours per day, similar to what teachers clock daily in a classroom (Hunter and Titze, 2010). The radiated acoustic energy emitted per day (power times vocalization time) would then be 1.0 W × 2h × 3600 s = 7,200 J (Joules). This is about 0.1% of the caloric intake of 8.37 million Joules. Long and loud vocalization would therefore appear not to be a drain on available energy in humans. Even if the combined efficiency of converting metabolic energy to muscle contraction and converting aerodynamic energy into acoustic energy is less than 1%, long and loud vocalization would still only assume about 10% of the daily caloric energy intake. Thus, the hot dogs and hamburgers at a football game are enough to sustain vocalization for hours, assuming there is no vocal injury with shouting. For context, a hot dog with a bun offers about 300 kcal, or 1.2 million Joules.

The same cannot be said about vocalization across species. For birds, energy considerations are critical. An 80 g Piha bird consumes on the order of 25 kcal per day, or 104,600 Joules (Lasiewski & Dawson, 1967). The energy requirements for long periods of vocalization may be a significant portion of this caloric intake. It has been reported that the Piha “qui” scream has a sound level of about 110 dB at a distance of 1.0 m (Suzuki et al., 2020). If the inverse square law were applicable, the radiated acoustic power output for this sound level would be 1.3 W. Assuming the bird vocalizes about 2000 s per day (1.5 s per call, 5 calls per min over a 6-hour period), the acoustic energy emitted would be 2,700 Joules. This is on the order of 3% of the daily caloric input of the bird. If the efficiency of converting muscular and aerodynamic energy to acoustic energy were only around 1%, as in human speech (Schutte, 1980), the energy required for vocalization would be 270,000 J, more than twice the daily caloric intake of the bird. Where is the error in the calculation? The answer lies in the efficiency of sound production and radiation.

Consider first the frequency of the “qui” syllables. Figure 3 shows a spectrogram of a typical Piha call that is repeated many times a day (Bird Jamboree Video Recording, 2022). In the two-syllable “qui” segment in the middle, the fundamental frequency glides from about 4000 to 5000 Hz. Several harmonics are also visible.

For this vocalization, it is evident that either a much higher efficiency is achieved by the bird than by humans, or the SPL measurement does not reflect the correct radiated acoustic power. The bird’s aerodynamic power is estimated to be 16 mW, based on a 2.0 kPa lung pressure, a 12 cm³ expiratory volume, and a mean airflow rate of 8.0 cm³/s in a 1.5 s scream (Nemeth, 2004). So, the question becomes: how can 1.3 W of acoustic power be produced with only 16 mW of aerodynamic power? Even if 100% of the aerodynamic power were converted to acoustic power and radiated from the beak with 100% efficiency, the SPL at 1.0 m would only be 91 dB. For comparison with other animal vocalizations, calls from blue monkeys have been recorded in the range of 62–100 dB at 1 m (Brown, 1989). A lion roar is on the order of 110 dB at 1.0 m distance (Weissengruber, 2002). Dog barks are typically in the 90–100 dB range at 1.0 m, but intense barks can reach 110 dB (Yin & McCowan, 2004). These mammals can produce much greater aerodynamic power than the Piha bird. What is the secret in this bird vocalization?

The Piha: Master of radiation efficiency

We suggest that radiation from the beak cannot be isotropic, or spherical around the head. It must be a beam of sound with directivity along an axis. This is possible with high frequency and use of the whole body as a baffle (Titze and Palaparthi, 2018). A baffle is a surface that reflects backward propagating sound, reversing its direction. More sound goes forward than backwards or sideways. With such directivity, sound along the primary axis can range from 10 to 30 dB above that for isotropic radiation (Titze and Palaparthi, 2018).

The sound level of 110 dB at 1.0 m for the Piha was extrapolated from greater distances (> 8 m) via the inverse-square law (sound radiating spherically from a localized source) (Nemeth, 2004). With a fundamental frequency of 4–5 kHz, a wide beak opening, and the head retracted to create a nearly spherical baffle, the radiation efficiency could reach nearly 100% according to theoretical predictions by Titze and Palaparthi (2018). In comparison, the above authors determined an optimal radiation efficiency in humans. With a human head radius of 9 cm, a mouth radius of 2 cm, and a frequency of 5000 Hz, the radiation efficiency could reach 50%. Considerable directivity in the radiation pattern will occur at that frequency, especially if the head is retracted. Furthermore, if the aerodynamic power from the lungs is converted to acoustic power at the glottis with an efficiency of at least 10%, then the overall efficiency is 5%, and the bird will expend only about 10% of its caloric intake for vocalization.

Conclusions

Humans cannot compete with the Piha and many other birds in producing a loud yell or scream. The limitation is attributed mainly to low fundamental frequency, but additional factors are a head that cannot be retracted into the body to form a baffle, a neck that cannot be bulged out, and a mouth opening that is too small for the head size.

Figure 4 shows the direction in which we need to adjust our body to scream like a Piha at a ball game. However, a frequency around 5000 Hz will be a whistle voice, which is not perceived as a loud call with the human auditory system. It might attract lots of birds to the stadium. So, we end with the question of the title: can we scream like a Piha bird at a ballgame? No, but we can honor and respect the variety of vocalizations nature has allowed us to enjoy.

References

Bird Jamboree. (2022, July 2). Screaming piha doing its loud call [Video]. YouTube. https://www.youtube.com/watch?v=Kg7Jl-jAdAM

Brown, C. H. (1989). The measurement of vocal amplitude and vocal radiation pattern in blue monkeys and grey-cheeked mangabeys. Bioacoustics, 1(3), 253–271.

Hunter, E. J., & Titze, I. R. (2010). Variations in intensity, fundamental frequency, and voicing for teachers in occupational versus nonoccupational settings.

Lasiewski, R. C., & Dawson, W. R. (1967). A re-examination of the relation between standard metabolic rate and body weight in birds. The Condor, 69(1), 13–23.

Németh, E. (2004). Measuring the sound pressure level of the song of the screaming piha (Lipaugus vociferans): One of the loudest birds in the world? Bioacoustics, 14(3), 225–228.

OpenAI. (2026). Comic-style illustration of a man representing the screaming piha bird mouth position with exaggerated posture [AI-generated image]. ChatGPT. https://chat.openai.com/

Ricky’s Gadgets. (2025, July 7). Screaming piha bird at the San Diego Zoo [Video]. YouTube. https://www.youtube.com/watch?v=JQpRGbZHxrI

Schutte, H. K. (1980). The efficiency of voice production. State University Hospital, The Netherlands.

Suzuki, I., Fearnside, N., Tori, W., & Pareja, J. I. (2020). Screaming piha (Lipaugus vociferans) (Version 1.0). In T. S. Schulenberg (Ed.), Birds of the World. Cornell Lab of Ornithology. https://doi.org/10.2173/bow.scrpih1.01

Titze, I. R., & Palaparthi, A. (2018). Radiation efficiency for long-range vocal communication in mammals and birds. The Journal of the Acoustical Society of America, 143(5), 2813–2824. https://doi.org/10.1121/1.5032245

Weissengruber, G. E., Forstenpointner, G., Peters, G., Kübber-Heiss, A., & Fitch, W. T. (2002). Hyoid apparatus and pharynx in the lion (Panthera leo), jaguar (Panthera onca), tiger (Panthera tigris), cheetah (Acinonyx jubatus), and domestic cat (Felis silvestris f. catus). Journal of Anatomy, 201(3), 195–209. https://doi.org/10.1046/j.1469-7580.2002.00088.x

Yin, S., & McCowan, B. (2004). Barking in domestic dogs: Context specificity and individual identification. Animal Behaviour, 68(2), 343–355. https://doi.org/10.1016/j.anbehav.2003.07.016

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