Behaviors produced by a variety of sounds among eagles: A study with survival implications

JoAnn McGee –

University of Minnesota
75 East River Parkway
Minneapolis, MN 55455
United States

Christopher Feist
Christopher Milliren
Lori Arent
Julia B. Ponder
Peggy Nelson
Edward J. Walsh

Popular version of 3aABb4 – Behavioral responses of bald eagles (Haliaeetus leucocephalus) to acoustic stimuli in a laboratory setting
Presented at the 184 ASA Meeting
Read the abstract at

The ultimate goal of this project is to protect eagles by discouraging these charismatic birds from entering the airspace of wind energy facilities. The specific question under consideration centers on whether or not an acoustic cue, a sound, can be used for that purpose, to steer eagles away from harm’s way. Our specific goal in this particular study was to take the next step along our overall research path and determine if behaviors of bald eagles in particular were affected by different sound stimuli in a controlled laboratory environment.

Perhaps to be expected, behavioral responses varied significantly. Some birds explored their immediate airspace avidly, while others exhibited a more restrained set of behavioral responses to sound stimulation.

To get a feeling for the task, consider the reaction of this eagle to a sound stimulus in a quiet laboratory setting .

To collect these data, a bird was placed in a sound-damped room and the experiment was conducted from a control center just outside the exposure space. Birds were videotaped as sounds were delivered to one of two speakers and a group of unbiased judges was asked to determine (1) whether the bird responded to the sound based on its behavior, (2) to qualitatively assess the strength of the response, and (3) to identify the behaviors associated with the response. Twelve sounds were tested and judges were instructed to observe the eagle during a specified time window without knowing which sound, if any, had been played. Spectrograms of the sounds tested are shown in the figure.

By far the most common response was an attempt to localize the sound source based on head turning toward a speaker, although birds also frequently tilted their heads in response to stimuli. Females were slightly more responsive to sound stimuli than males, and not surprisingly, stimuli that elicited a higher number of responses also elicited stronger or more evident responses. Complex and natural sounds, for example, sounds produced by eagles, eaglets and pesky mobbing crow sounds, elicited more and stronger responses than man-made stimuli. Generally, bald eagles were fairly accurate in locating the direction that the sound originated, and, as before, females performed better than males.

The results from this study provide a critical step in an effort to protect eagles as we move away from the use of fossil fuels and rely more on wind power. We come away from this study with a better understanding of the types of sound signals that elicit more and stronger responses in bald eagles, and with the confidence that we will be able to objectively assess behavioral responses in more natural settings. We now know what these magnificent birds can hear, and we know that certain sound stimuli are more effective than others in evoking behavioral responses, taking us one step closer to our ultimate goal, to save bald eagles from undesirable outcomes and to give wind facility developers the tools needed to manage their facilities in an even more eco-friendly manner.

3aAB7 – Construction Noise Impact on Wild Birds

Pasquale Bottalico, PhD. –

Voice Biomechanics and Acoustics Laboratory
Department of Communicative Sciences and Disorders
College of Communication Arts & Sciences
Michigan State University
1026 Red Cedar Road
East Lansing, MI 48824

Popular version of paper 3aAB7, “Construction noise impact on wild birds”
Presented Tuesday morning, May 25, 2016, 10:20, Salon I
171st ASA Meeting, Salt Lake City

Almost all bird species use acoustic signals to communicate or recognize biological signals – to mate, to detect the sounds of predators and/or prey, to perform mate selection, to defend their territory, and to perform social activities. Noise generated from human activities (in particular by infrastructure and construction sites) has a strong impact on the physiology and behaviour of birds. In this work, a quantitative method for evaluating the impact of noise on wild birds is proposed. The method combines the results of previous studies that considered the effect of noise on birds and involved noise mapping evaluations. A forecast noise simulation was used to generate maps of (1) masking-annoyance areas and (2) potential density variation.

An example of application of the masking-annoyance areas method is shown in Figure 1. If a bird is in the Zone 1 (in purple), traffic noise and construction noise can potentially result in hearing loss and threshold shift. A temporary elevation of the bird’s hearing threshold and a masking of important communication signals can occur in the Zone 2 (in red). Zone 3 (in orange), 4 (in yellow) and 5 (in light green) are characterized by a high, medium and low level of signal masking, respectively. Once the level of noise generated by human activities falls below ambient noise levels in the critical frequencies for communication (2–8 kHz), masking of communication signals is no longer an issue. However, low-frequency noise, such as the rumble of a truck, may still potentially cause other behavioural and/or physiological effects (Zone 6, in green). No effects of any kind occur on the birds in Zone 7 (in dark green). The roles for Zone definition are based on the results of Dooling and Popper. [1]

Bottalico- Birds 1

Figure 1 Mapping of the interaction areas of noise effect on birds within the 7 zones for a project without (a) and with mitigations (b).

Waterman et al. [2] and Reijnem et al. [3-4-5] proposed a trend of the potential variation in birds density in relationship with the noise levels present in the area. This trend shows no effect on density when the noise levels are lower than 45 dB(A), while there is a rapid decrease (with a quadratic shape) for higher levels. An example of the potential decrease in bird density for a project with and without mitigations is shown in Figure 2. The blue areas are the areas where the birds’ density is not influenced by the noise, while the red ones are the areas from where the birds are leaving because the noise levels are too high.

This methodology permits a localization of the areas with greater impacts on birds. The mitigation interventions should be focused on these areas in order to balance bird habitat conservation and human use of land.

Bottalico- Birds 2

Figure 2 Potential decrease in bird density for a project without (a) and with mitigations (b).



  1. R. J. Dooling and A. N. Popper, The effects of highway noise on birds, Report prepared for The California Department of Transportation Division of Environmental Analysis, (2007).
  2. E. Waterman, I. Tulp, R. Reijnen, K. Krijgsveld and C. ter Braak, “Noise disturbance of meadow birds by railway noise”, Inter-Noise2004, (2004).
  3. R. Reijnen and R. Foppen, “The effects of car traffic on breeding bird populations in woodland. IV. Influence of population size on the reduction of density close to the highway”, J. Appl. Ecol. 32(3), 481-491, (1995).
  4. R. Reijnen, R. Foppen, C. ter Braak and J. Thissen, “The effects of car traffic on breeding bird populations in Woodland. III. Reduction of density in relation to the proximity of main roads”, J. Appl. Ecol. 32(1), 187-202, (1995).
  5. R. Reijnen, G. Veenbaas and R. Foppen, Predicting the Effects of Motorway Traffic on Breeding Bird Populations. Ministry of Transport and Public Works, Delft, Netherlands, (1995).

4aAB2 – Seemingly simple songs: Black-capped chickadee song revisited

Allison H. Hahn –
Christopher B. Sturdy –

University of Alberta
Edmonton, AB, Canada

Popular version of 4aAB2 – Seemingly simple songs: Black-capped chickadee song revisited
Presented Thursday morning, November 5, 8:55 AM, City Terrace Room
170th ASA Meeting, Jacksonville, Fl

Vocal communication is a mode of communication important to many animal species, including humans. Over the past 60 years, songbird vocal communication has been widely-studied, largely because the invention of the sound spectrograph allows researchers to visually represent vocalizations and make precise acoustic measurements. Black-capped chickadees (Poecile atricapillus; Figure 1) are one example of a songbird whose song has been well-studied. Black-capped chickadees produce a short (less than 2 seconds), whistled fee-bee song. Compared to the songs produced by many songbird species, which often contain numerous note types without a fixed order, black-capped chickadee song is relatively simple, containing two notes produced in the same order during each song rendition. Although the songs appear to be acoustically simple, they contain a rich variety of information about the singer including: dominance rank, geographic location, and individual identity [1,2,3].

Interestingly, while songbird song has been widely-examined, most of the focus (at least for North Temperate Zone species) has been on male-produced song, largely because it was thought that only males actually produced song. However, more recently, there has been mounting evidence that in many songbird species, both males and females produce song [4,5]. In the study of black-capped chickadees, the focus has also been on male-produced song. However, recently, we reported that female black-capped chickadees also produce fee-bee song. One possible reason that female song has not been extensively reported is that to human vision, male and female chickadees are visually identical, so females that are singing may be mistakenly identified as male. However, by identifying a bird’s sex (via DNA analysis) and recording both males and females, our work [6] has shown that female black-capped chickadees do produce fee-bee song. Additionally, these songs are overall acoustically similar to male song (songs of both sexes contain two whistled notes; see Figure 2), making vocal discrimination by humans difficult.

Our next objective was to determine if any acoustic features varied between male and female songs. Using bioacoustic techniques, we were able to demonstrate that there are acoustic differences in male and female song, with females producing songs that contain a greater frequency decrease in the first note compared to male songs (Figure 2). These results demonstrate that there are sufficient acoustic differences to allow birds to identify the sex of a signing individual even in the absence of visual cues. Because birds may live in densely wooded environments, in which visual, but not auditory, cues are often obscured, being able to identify the sex of a bird (and whether the singer is a potential mate or territory rival) would be an important ability.

Following our bioacoustic analysis, an important next step was to determine whether birds are able to distinguish between male and female songs. In order to examine this, we used a behavioral paradigm that is common in animal learning studies: operant conditioning. By using this task, we were able to demonstrate that birds can distinguish between male and female songs; however, the particular acoustic features birds use in order to discriminate between the sexes may depend on the sex of the bird that is listening to the song. Specifically, we found evidence that male subjects responded based on information in the song’s first note, while female subjects responded based on information in the song’s second note [7]. One possible reason for this difference in responding is that in the wild, males need to quickly respond to a rival male that is a territory intruder, while females may assess the entire song to gather as much information about the singing individual (for example, information regarding a potential mate’s quality). While the exact function of female song is unknown, our studies clearly indicate that female black-capped chickadees produce songs and the birds themselves can perceive differences between male and female songs.

Black-capped chickadee
Figure 1. An image of a black-capped chickadee.

Figure 2. Spectrogram (x-axis: time; y-axis: frequency in kHz) on a male song (top) and female song (bottom).

Sound file 1. An example of a male fee-bee song.

Sound file 2. An example of a female fee-bee song.


  1. Hoeschele, M., Moscicki, M.K., Otter, K.A., van Oort, H., Fort, K.T., Farrell, T.M., Lee, H., Robson, S.W.J., & Sturdy, C.B. (2010). Dominance signalled in an acoustic ornament. Animal Behaviour, 79, 657–664.
  2. Hahn, A.H., Guillette, L.M., Hoeschele, M., Mennill, D.J., Otter, K.A., Grava, T., Ratcliffe, L.M., & Sturdy, C.B. (2013). Dominance and geographic information contained within black-capped chickadee (Poecile atricapillus) song. Behaviour, 150, 1601-1622.
  3. Christie, P.J., Mennill, D.J., & Ratcliffe, L.M. (2004). Chickadee song structure is individually distinctive over long broadcast distances. Behaviour 141, 101–124.
  4. Langmore, N.E. (1998). Functions of duet and solo songs of female birds. Trends in Ecology and Evolution, 13, 136–140.
  5. Riebel, K. (2003). The “mute” sex revisited: vocal production and perception learning in female songbirds. Advances in the Study of Behavior, 33, 49–86
  6. Hahn, A.H., Krysler, A., & Sturdy, C.B. (2013). Female song in black-capped chickadees (Poecile atricapillus): Acoustic song features that contain individual identity information and sex differences. Behavioural Processes, 98, 98-105.
  7. Hahn, A.H., Hoang, J., McMillan, N., Campbell, K., Congdon, J., & Sturdy, C.B. (2015). Biological salience influences performance and acoustic mechanisms for the discrimination of male and female songs. Animal Behaviour, 104, 213-228.

1pABa2 – Could wind turbine noise interfere with greater prairie chicken (tympanuchus cupido pinnatus) courtship?

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

Cara E. Whalen –
Larkin A. Powell –
Mary Bomberger Brown –
School of Natural Resources
University of Nebraska-Lincoln
Lincoln, NE 68583

Popular version of paper 1pABa2 Hearing sensitivity in the Greater Prairie Chicken
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.

Click here to listen to the hum

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.

Watch the video clip below to observe the courtship display

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).

FIGURE 1 (file missing): Acoustics Characteristics of the “BOOM”

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.

FIGURE 2 (file missing): ABR Waveforms

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.

FIGURE 3 (file missing): Audiogram and wind turbine noise

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.

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.