Edward J. Walsh – Edward.Walsh@boystown.org
JoAnn McGee – JoAnn.McGee@boystown.org
Boys Town National Research Hospital
555 North 30th St.
Omaha, NE 68131

Cara E. Whalen – carawhalen@gmail.com
Larkin A. Powell – lpowell3@unl.edu
Mary Bomberger Brown – mbrown9@unl.edu
School of Natural Resources
University of Nebraska-Lincoln
Lincoln, NE 68583

Popular version of paper 1pABa2
Presented Monday afternoon, May 18, 2015
169th ASA Meeting, Pittsburgh

The Sand Hills ecoregion of central Nebraska is distinguished by rolling grass-stabilized sand dunes that rise up gently from the Ogallala aquifer. The aquifer itself is the source of widely scattered shallow lakes and marshes, some permanent and others that come and go with the seasons.
However, the sheer magnificence of this prairie isn’t its only distinguishing feature. Early on frigid, wind-swept, late-winter mornings, a low pitched hum, interrupted by the occasional dawn song of a Western Meadowlark (Sturnella neglecta) and other songbirds inhabiting the region, is virtually impossible to ignore.

The hum is the chorus of the Greater Prairie Chicken (Tympanuchus cupido pinnatus), the communal expression of the courtship song of lekking male birds performing an elaborate testosterone-driven, foot-pounding ballet that will decide which males are selected to pass genes to the next generation; the word “lek” is the name of the so-called “booming” or courtship grounds where the birds perform their wooing displays.
While the birds cackle, whine, and whoop to defend territories and attract mates, it is the loud “booming” call, an integral component of the courtship display that attracts the interest of the bioacoustician – and the female prairie chicken.

The “boom” is an utterance that is carried long distances over the rolling grasslands and wetlands by a narrow band of frequencies ranging from roughly 270 to 325 cycles per second (Whalen et al., 2014). It lasts about 1.9 seconds and is repeated frequently throughout the morning courtship ritual.
Usually, the display begins with a brief but energetic bout of foot stamping or dancing, which is followed by an audible tail flap that gives way to the “boom” itself.

For the more acoustically and technologically inclined, a graphic representation of the pressure wave of a “boom,” along with its spectrogram (a visual representation showing how the frequency content of the call changes during the course of the bout) and graphs depicting precisely where in the spectral domain the bulk of the acoustic power is carried is shown in Figure 1. The “boom” is clearly dominated by very low frequencies that are centered on approximately 300 Hz (cycles per second).

Vocalization is, of course, only one side of the communication equation. Knowing what these stunning birds can hear is on the other.
We are interested in what Greater Prairie Chickens can hear because wind energy developments are encroaching onto their habitat, a condition that makes us question whether noise generated by wind turbines might have the capacity to mask vocal output and complicate communication between “booming” males and attending females.
Step number one in addressing this question is to determine what sounds the birds are capable of hearing – what their active auditory space looks like. The golden standard of hearing tests are behavioral in nature – you know, the ‘raise your hand or press this button if you can hear this sound’ kind of testing. However, this method isn’t very practical in a field setting; you can’t easily ask a Greater Prairie Chicken to raise its hand, or in this case its wing, when it hears the target sound.
To solve this problem, we turn to electrophysiology – to an evoked brain potential that is a measure of the electrical activity produced by the auditory parts of the inner ear and brain in response to sound. The specific test that we settled on is known as the ABR, the auditory brainstem response.
The ABR is a fairly remarkable response that captures much of the peripheral and central auditory pathway in action when short tone bursts are delivered to the animal. Within approximately 5 milliseconds following the presentation of a stimulus, the auditory periphery and brain produce a series of as many as five positive-going, highly reproducible electrical waves. These waves, or voltage peaks, more or less represent the sequential activation of primary auditory centers sweeping from the auditory nerve (the VIIIth cranial nerve), which transmits the responses of the sensory cells of the inner ear rostrally, through auditory brainstem centers toward the auditory cortex.
Greater Prairie Chickens included in this study were captured using nets that were placed on leks in the early morning hours. Captured birds were transported to a storage building that had been reconfigured into a remote auditory physiology lab where ABRs were recorded from birds positioned in a homemade, sound attenuating space – an acoustic wedge-lined wooden box.

The waveform of the Greater Prairie Chicken ABR closely resembles ABRs recorded from other birds – three prominent positive-going electrical peaks, and two smaller amplitude waves that follow, are easily identified, especially at higher levels of stimulation. In Figure 2, ABR waveforms recorded from an individual bird in response to 2.8 kHz tone pips are shown in the left panel and the group averages of all birds studied under the same stimulus conditions are shown in the right panel; the similarity of response waveforms from bird to bird, as indicated in the nearly imperceptible standard errors (shown in gray), testifies to the stability and utility of the tool. As stimulus level is lowered, ABR peaks decrease in amplitude and occur at later time points following stimulus onset.
Since our goal was to determine if Greater Prairie Chickens are sensitive to sounds produced by wind turbines, we generated an audiogram based on level-dependent changes in ABRs representing responses to tone pips spanning much of the bird’s audiometric range (Figure 3). An audiogram is a curve representing the relationship between response threshold (i.e., the lowest stimulus level producing a clear response) and stimulus frequency; in this case, thresholds were averaged across all animals included in the investigation.

As shown in Figure 3, the region of greatest hearing sensitivity is in the 1 to 4 kHz range and thresholds increase (sensitivity is lost) rapidly at higher stimulus frequencies and more gradually at lower frequencies. Others have shown that ABR threshold values are approximately 30 dB higher than thresholds determined behaviorally in the budgerigar (Melopsittacus undulates) (Brittan-Powell et al., 2002). So, to answer the question posed in this investigation, ABR threshold values were adjusted to estimate behavioral thresholds, and the resulting sensitivity curve was compared with the acoustic output of a wind turbine farm studied by van den Berg in 2006. The finding is clear; wind turbine noise falls well within the audible space of Greater Prairie Chickens occupying booming grounds in the acoustic footprint of active wind turbines.
While findings reported here indicate that Greater Prairie Chickens are sensitive to at least a portion of wind turbine acoustic output, the next question that we plan to address will be more difficult to answer: Does noise propagated from wind turbines interfere with vocal communication among Greater Prairie Chickens courting one another in the Nebraska Sand Hills? Efforts to answer that question are in the works.

Presentation #1pABa2 “Hearing sensitivity in the Greater Prairie Chicken” by Edward J. Walsh, Cara Whalen, Larkin Powell, Mary B. Brown, and JoAnn McGee will be take place on Monday, May 18, 2015, at 1:15 PM in the Rivers room at the Wyndham Grand Pittsburgh Downtown Hotel. The abstract can be found by searching for the presentation number here:

tags: chickens, mating, courtship, hearing, Nebraska, wind turbines

Brittan-Powell, E.F., Dooling, R.J. and Gleich, O. (2002). Auditory brainstem responses in adult budgerigars (Melopsittacus undulates). J. Acoust. Soc. Am. 112:999-1008.
van den Berg, G.P. (2006). The sound of high winds. The effect of atmospheric stability on wind turbine sound and microphone noise. Dissertation, Groningen University, Groningen, The Netherlands.
Whalen, C., Brown, M.B., McGee, J., Powell, L.A., Smith, J.A. and Walsh, E.J. (2014). The acoustic characteristics of greater prairie-chicken vocalizations. J. Acoust. Soc. Am. 136:2073.

1aAB4 – What does a Greater Prairie-Chicken sound like? It’s not your typical cock-a-doodle-doo! – Cara Whalen

It is 5 o’clock in the morning and only a hint of sunlight is visible on the horizon. Besides the sound of a light breeze swirling through the grass, all is quiet on the Nebraska prairie. Everything seems to be asleep. Then, suddenly, “whhooo-doo-doooohh” breaks the silence. The prairie-chickens have arrived.

The Greater Prairie-Chicken is a medium-sized grouse that lives on the prairies of central North America (Figure 1a) (Schroeder and Robb 1993). Prairie-chickens are well-known for their breeding activities in which the males congregate in groups each spring and perform elaborate courtship displays to attract females (Figure 1b). The areas where the males gather, called “leks,” are distributed across the landscape. Female prairie-chickens visit leks every morning to observe and compare males until a suitable one is chosen. After mating, females leave the leks to nest and raise their broods on their own, while the males remain on the leks and continue to perform courtship displays. Click the link to watch a video clip of prairie chickens lekking.

whalen_figure_1a whalen_figure_1b

Figure 1a: A male Greater Prairie-Chicken. Figure 1b: A male prairie-chicken performs a courtship display for a female.

These complex courtship behaviors do not occur in silence. Vocalization plays an important role in the mate choice behavior of prairie-chickens. As part of a larger study addressing the effects of electricity producing wind turbine farms on prairie-chicken ecology, we wanted to learn more about the acoustic properties of prairie-chicken calls. We did this by recording the sound of prairie-chicken vocalizations at leks in the Nebraska Sandhills. We visited the leks in the very early morning and set up audio recorders, which were placed close enough to prairie-chickens on their leks to obtain high quality recordings (Figure 2a). Sitting in a blind at the edges of leks (Figure 2b), we observed prairie-chickens while they were lekking and collected the audio recordings.


Figure 2a: We used audio recorders to record male prairie-chicken vocalizations at the leks. Figure 2b: We observed lekking prairie-chickens and recorded vocalizations by sitting in a blind at the edge of a lek.

Male Greater Prairie-Chickens use four prominent vocalizations while on the leks: the “boom,” “cackle,” “whine” and “whoop.” The four vocalizations are distinct and serve different purposes.

The boom is used as part of the courtship display, so one function is to attract mates. Booms travel a long distance across the prairie, so another purpose of the call is to advertise lek location to other prairie-chickens (Sparling 1981, 1983). Click to listen to a boom sound clip

or to watch a boom video clip we recorded at the leks.

The “cackles” are short calls typically given in rapid succession. Prairie-chickens use the cackle as an aggressive or territorial call (Sparling 1981, 1983) or as a warning to alert other prairie-chickens of potential danger, such as an approaching prairie falcon, coyote or other predator. Click to listen to a cackle sound clip.

The “whine” is slightly longer in duration than the cackle; whines and cackles are often used together. The purpose of the whine is similar to that of the cackle. It serves as an aggressive and territorial call, although it is thought that whines are somewhat less aggressive than cackles (Sparling 1981, 1983). Click to listen to a whine sound clip

or to watch a video clip of cackles and whines (the cackles are the shorter notes and the whines are the longer notes).

The “whoop” is used for mate attraction. Males typically use the whoop when females are present on the lek (Sparling 1981, 1983). Click to listen to a whoop sound clip

or to watch a whoop video clip.

We measured acoustic characteristics of the vocalizations captured on the recordings so we could evaluate their features in detail. We are using this information about the vocalizations in a study of the effects of wind turbine sound on Greater Prairie-Chickens (Figure 3). We hope to determine whether the vocalizations produced by prairie-chickens near a wind farm are different in any way from those produced by prairie-chickens farther away. For example, do the prairie chickens near wind turbines call at a higher pitch in response to wind turbine sound? Also, do the prairie chickens near wind turbines vocalize louder? Ultimately we would like to know if components of the prairie-chickens’ vocalizations are masked by the sounds of the wind turbines.


Figure 3: We are conducting a study of the effects of wind turbine noise on Greater Prairie-Chickens.


The effect of anthropogenic noise is an issue not limited to Greater Prairie-Chickens and wind turbines. As humans create increasingly noisy landscapes through residential and industrial development, vehicle traffic, air traffic and urban sprawl, the threats posed to birds and other wildlife are likely to be significant. It is important to be aware of the potential effects of anthropogenic sound and find ways to mitigate those effects as landscapes become noisier.



Schroeder, M. A., and L. A. Robb. 1993. Greater Prairie-Chicken (Tympanuchus cupido). In The Birds of North America, no. 36 (A. Poole, P. Stettenheim, and F. Gill, Eds.). Academy of Natural Sciences, Philadelphia, and American Ornithologists’ Union, Washington, D.C.

Sparling, D. W. 1981. Communication in prairie grouse. I. Information content and intraspecific functions of principal vocalizations. Behavioral and Neural Biology 32:463-486.

Sparling, D. W. 1983. Quantitative analysis of prairie grouse vocalizations. Condor 85:30-42.


Cara Whalen – cara.whalen@huskers.unl.edu

Mary Bomberger Brown – mbrown9@unl.edu
Larkin Powell – lpowell3@unl.edu
Jennifer Smith – jsmith60@unl.edu
University of Nebraska – Lincoln

School of Natural Resources
3310 Holdrege Street
Lincoln, NE 68583


Edward J. Walsh – Edward.Walsh@boystown.org
JoAnn McGee – JoAnn.McGee@boystown.org
Boys Town National Research Hospital
555 N. 30th Street
Omaha, NE 68131


Popular version of paper 1aAB4

Presented Monday morning, October 27th, 2014

168th ASA Meeting, Indianapolis