Communication breakdown! Signal modality drives the effect of information loss on the behavioral responses of the threatened Great-Billed Seed-Finch, Sporophila maximiliani (Thraupidae: Passeriformes)

doi:10.21203/rs.3.rs-3809626/v1

Communication is a central process in animals' interactions and the transmission of information depends on the signal quality. As signals degrade, the resulting loss of information has the potential to increase the ambiguity about the sender’s motivation and status. Thus, the information loss can generate in the receptor a state of motivational conflict and increases the aggressiveness as a coping strategy. We tested whether the information loss affects the behavioral response of Sporophila maximilianiusing (i) a playback experiment, to simulate an acoustic signal, and (ii) a mirror experiment, to simulate a visual signal. We found that a greater degradation of the acoustic signal induced in males’ calls a modulation from lower to higher frequencies, indicating a fear state. Conversely, the degradation of visual signal resulted in an equally high emission of displacement activity in relation to total visual information context, showing no effect of the signal interference. Also, we detected that an increase in the background noise, more than the loss of information, resulted in an increase of the emission of displacement activities and calls of lower frequency, indicating stressful and aggressive states, respectively. So, the response of S. maximiliani to information interference was modulated by the signal modality. The great interference in acoustic signals results in a fear state due to the ambiguity of the interaction context, suggesting that a partially comprehensible signal is more harmful than a totally degraded one. The emission of maintenance behaviors as displacement activities is an indicator of the higher stress endured by the individuals exposed to visual signals, independent of interferences on signal quality. Furthermore, the negative effect of artificial environmental noise can be high, suggesting some level of neophobia in S. maximiliani.

signal interference

loss of information

motivational conflict

displacement activity

fear

behavioral changes

Communication can be defined as the exchange of information between individuals, a sender and a receiver (Sebeok 1968), who must be able to decode this message and emit a response (Maynard-Smith and Harper 2003; Vielliard and Silva 2010). These signals can be acoustic, visual, or chemical (Marques 2008), sometimes involving more than one modality (multimodal signals) (Smith 1977). Both type and structure of these messages could be affected by the environment and social context (Morton 1977; Smith et al. 2011; Velásquez et al. 2018). Therefore, communication is a co-evolutionary process between a sender, which encodes any kind of information in the signaling parameters, and a receiver, which must have the ability to decode the message in the signal (Font and Carazo 2010; Seyfarth et al. 2010).

Environmental factors and context impose the evolutionary pressure that drives signals adaptation or changes that maintain the integrity of the information coded (Morton 1977). For example, information could be encoded using different signaling modalities, in which one message is transmitted in two distinct ways as a backup that reduces the chance of information loss (signal backup hypotheses, Møller and Pomiankowski 1993). Birds (Smith et al. 2011), primates (Frohlich et al. 2019) and anurans (Starnberger et al. 2014) could use redundant multimodal communication. Also, the use and relevance of a signal modality may vary according to other characteristics, such as in high colonial density, where visual communication may be the most effective and may lead to the lower confusion during communication (Marler 1957). Another way to prevent the information loss is through signal plasticity, which allows changes in signal according to social and environmental conditions, minimizing the interference of noise and other external factors in signal transmission (Cynx et al. 1998; Grabarczyk et al. 2020). Among birds, which have a complex acoustic communication system, the adaptation of vocalization to habitat changes and noises is common, including changes in song parameters such as frequency, duration, and intensity (Lombard 1911; Cynx et al. 1998; Brumm and Todt 2002; Hansen et al. 2005, Nemeth and Brumm 2010; Luther et al. 2016).

However, what does occur when the information loss can not be avoided? Experimental evidence, in a territorial defense context, showed that resident anuran males could adjust their emission of aggressive acoustic signals based on images of intruder males, but the increase in the aggressive behavior was larger when the image was partially obstructed (Furtado and Nomura 2014). Failure in the communication process can impair risk assessment of competitor strength. For example, individuals emitting acoustic signals are displaying their physical status both to attract females and to repel male competitors (Gerhardt 1992; Brumm and Todt 2004; Seyfarth et al. 2010). When the signal is hampered, due to environmental noise, the evaluation of the information about the sender is also hampered and the receiver must deal with the fragment of information available. Potentially, this effect can affect the individual decision-making (i.e, evaluation the strength of a potential competitor or the quality of a mate), generating a motivational conflict, which is a state in which the individual does not have enough information about the context, hesitating about what should be the best behavior to display (Benus et al. 1991; Santarém and Silva 1999). In this circumstance, the uncertainty about information received, due to signal degradation or other effects, could increase anxiety levels, which have already been demonstrated for mammals and anura (Choi et al. 2022; Furtado and Nomura 2014).

Anxiety can be defined as an animal and human state in which bodily changes occur to prepare the individual for possible situations of threat to their survival or well-being (Steimer 2002). Anxiety is not necessarily a negative state, once it prepares the individual to cope with an unpredictable situation, by inducing the emission of behaviors that are useful to cope with the stimulus generating anxiety (Steimer 2002). For example, anxiety can lead to an increase in the display of alert and aggressive behaviors due to the possibility of a dangerous outcome (Maestripieri et al. 1992; Steimer 2002). This behavioral path, controlled by anxiety, is sometimes called an active coping strategy (Benus et al. 1991; Koolhaas et al. 1999), and aggressiveness seems to be a common active coping strategy when an individual is exposed to a motivational conflict context (Bolhuis et al. 2005; Hurd 2006; Koolhaas et al. 2007; Furtado and Nomura 2014; Senar et al. 2017). However, anxiety can also elicit nonintentional behaviors, called displacement activities, whose function is not related to the context in which the behavior is emitted (Tinbergen 1952). Displacement activities are generated when one stimulus ends up activating two antagonistic pathways simultaneously, like in a motivational conflict context (Falk 1977; Santarém and Silva 1999). In this state, the inability to display the two incompatible movements results in the release of energy by an irrelevant behavior (Zeigler 1964). Moreover, displacement activities seem to be species specific (Zeigler 1964), once the behavior released as displacement activity varies among species, as preening during courtship by duck species (Dawkins et al. 1991) or pacing displayed by mammals in captivity (Guy 2012).

Birds have a complex organ structure of sound production that allows the emission of a large diversity of calls and songs (Vielliard and Silva 2010). So, through vocalizations, birds exchange information at short and long distances about the environment (e.g., predation risk, food availability), about the individual, the group (Marques 2008) and the population (dialects) identity (Silva and Vielliard 2011), and also their fitness and motivation (Morton 1977). Because of that, birds are important animal models to study animal communication and the effect of environmental factors on signaling, as the effect of the increase in environmental noise, especially by anthropogenic causes (Nemeth et al. 2013; Grade and Sieving 2016; Curry et al. 2018; Grabarczyk and Gill 2020; Lenis and Ferreira 2020). In this study, we experimentally evaluated how incomplete information affects birds’ behavior during intra-specific communication. Specifically, we aimed to elucidate: i) whether the incomplete information can promote a motivational conflict, and ii) whether aggressiveness would be a preferential coping strategy in response to incomplete information. We expected that i) incomplete information can generate a motivational conflict context in birds, caused by the uncertainty about the result of an interaction (Maestripieri et al. 1992). Once the temporal and spectral properties of the acoustic signal carries information about the quality, health and motivation of the sender (Morton 1977; Marques 2008), the reduction of its accuracy could result in motivational conflict once risk assessment is hampered. The motivational conflict would be evidenced by the greater emission of displacement activity in partial information contexts, since the context of either complete or no information (strong degradation) would result in lower communication ambiguity for the receiver (Figure 1). Also, we expected that ii) aggressiveness would be readily used as a coping strategy, as we are simulating a territory dispute. Aggressiveness is a common behavior for territorial birds in contexts where the risk assessment is difficult (Onsal et al. 2022). To territorial owners, the cost of losing the territory in dispute is larger and the aggressiveness would be the most efficient coping strategy without an accurate evaluation of its competitor (Furtado and Nomura 2014) (Figure 1).

To test these hypotheses, we conducted an experiment with the Great-Billed Seed-Finch Sporophila maximiliani (Cabanis, 1851), known for its melodious song, complex vocal apparatus, and high learning capacity, being able to expand its vocal repertoire during its lifetime (Silva and Vielliard 2011). This bird is a territorial species that naturally presents an aggressive disposition to conspecifics, by displaying acoustic and visual signals in contexts of territorial defense, mating, and co-specific discrimination (Ubaid et al. 2018). These characteristics make the species a good model for understanding the effects of information loss on behavior. Furthermore, due to the historical removal of individuals from nature, little is known about their biology and there are only a few studies published about the species behavior. We secondarily contribute to the knowledge of the behavior of this endangered Brazilian songbird (Instituto Chico Mendes de Conservação da Biodiversidade [ICMBio] 2018; BirdLife International 2019). Thus, our work also provides information about their communication signals and behavior, that can be useful for conservation programs for the reintroduction of Sporophila maximiliani individuals into nature, such as Projeto Bicudos do Cerrado (Floresta Cheia Institute) and Projeto Bicudos (WAITA).

Study area and subjects

We conduct the experiments at the Centro de Triagem de Animais Silvestres – Goiás (CETAS-GO), located at Goiânia municipality (16°35’56” S, 49°11’55” W), Goiás State, Brazil. CETAS is a center directed by the Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais (IBAMA) and is responsible for the management and rehabilitation of wild animals that arrive through voluntary deliveries, apprehensions and rescue actions. The animals used in this work were provided by CETAS-GO, which houses the birds in adequate and individual cages, where they are constantly monitored by technicians and veterinarians responsible for its feeding and health care. We carried out all observations and experimental procedures from 5 to 28 of March/2022.

The Great-Billed Seed-Finch (S. maximiliani) is a Passeriforme of the Thraupidae family. Like other species of the genus Sporophila, the Great-Billed Seed-Finch is known as a “seed eater”, presenting a granivorous diet based mainly on seeds of Cyperaceae family, such as Hypolytrum pungens and Cyperus rotundus (Machado et al. 2020). This species lives in pairs and exhibits territorial behavior, especially during the reproductive period, which occurs between the months of September and April (Ubaid et al. 2018). This species is classified as Endangered by the IUCN red list (BirdLife International 2019) and Critically Endangered by the ICMBio (ICMBio 2018), with an estimate of less than 100 individuals in the wild (Ubaid et al. 2021). However, Brazil has a large number of legal and illegal breeders that kept this species in captivity due to its call and ex situ conservation purposes (Trajano and Carneiro 2019; Machado 2020). Thus, all individuals used in our experiments come from apprehensions of birds raised under illegal conditions, as well as from the donation of individuals by legalized breeders for conservation purposes (LAML Baptista, personal communication). All animals used in our observations were destined for the reintroduction program of individuals in natural areas developed by CETAS-GO and Projeto Bicudos do Cerrado (https://www.florestacheia.org.br/projetos).

General procedure

We conducted the acoustic and visual experiments with ten males and ten females not paired (N=20). We first submitted all individuals to the acoustic signaling model and then to the visual one. The experiment occurred with one animal at a time (Focal Animal method; Lehner 1987), in individual cages (45cm x 22cm x 30cm), at the times of greatest activity of the birds, that is, in the early morning, between 7am and 10am, and in the late afternoon, between 15pm and 18pm. The experimental arena was set up in a closed environment (6.3m x 5m x 3m), with a controlled temperature of 25°C. To evaluate individual responses, the same animal was subjected to each of the treatments, in a repeated measures procedure, and the order at which the focal animals were submitted to the treatments was previously randomized (Pereira et al. 2015).

Subjects were taken to the experimental arena at the time of each behavioral trial (acoustic and visual). We waited five minutes before starting the observation session to allow the focal animal an acclimatization period. Then, the five acoustic treatments were played or the three visual treatments were presented to the focal subject. We recorded the behavioral responses of the animal focal using a Sony® DCR-SX21 video camera and captured acoustic emissions in .WAV format using an AudioMoth® digital recorder, with a sampling rate of 48000 Hz and depth of 16dB.

Acoustic experiment

For the acoustic experiment we designed a playback experiment, in which we presented to individuals the only known song of natural populations of the species, that is used in territorial defense and courtship. The song was obtained from the Xeno-canto database of a unique individual to control for possible effects of song variation (Silva and Lima 2009). To simulate the signal quality loss, we overlapped different percentages of the song duration with artificial white noise, a wideband noise, using the software Audacity® v. 3.0 (Audacity Team 2021). In this manner, we simulated five levels of information degradation: signal with 100% of information (negative control), signal modified with 90% of information without white noise overlap (slightly degraded), signal with 75% of information without white noise overlap (moderately degraded), signal with 50% of information without white noise overlap (heavily degraded), and 0% of information that is the reproduction of white noise (positive control) (Figure 1a). All treatments had five minutes of duration, with an emission rate of 3 signal/min, similar to natural call, and were played at a sound pressure level of 70dB by a RedMi note 8 Pro cellphone located 1m away from the cage (Figure 1a). All individuals were exposed to all levels of acoustic signal degradation with five minutes of interval between treatments, totaling 50 minutes of acoustic assay. We expect greater emission of displacement activities and aggressive behavior in moderately degraded treatment, followed by moderately degraded treatment, because the ambiguity of information is bigger in these treatments (Figure 1a).

Visual experiment

We use a mirror (22x29 cm) to simulate a visual stimulus of a co-specific competitor (Figure 1b). Although there are no studies on the behavior of Great-Billed Seed-Finch in front of a mirror, most studies with birds show that they do not have the ability to self-recognize their images in the mirror (Kraft et al. 2017; Leitão et al. 2019; Lin et al. 2021), making the mirror a good model to simulate an intruder with the same size of the animal focal. We used a scotch tape to simulate visual barriers and to generate three levels of signal degradation: 100% of information, that is, the mirror unobstructed view (clear view); the mirror with a 50% area covered with a stripe pattern (partial obstructed view); and the mirror with all of its area covered (obstructed view) (Figure 1b). The mirror was placed 50 cm from the ground and 10 cm from the cage (Figure 1b). All individuals were exposed to all levels of visual signal degradation and the treatment had five minutes of duration, followed by five minutes of interval until presentation of the next treatment, totaling 30 minutes of visual assay. We expect greater emission of displacement activity in the partial obstructed view treatment because it is the only one that presents ambiguity of information (Figure 1b).

Data analyses

We obtained from the video recordings the frequency of emissions (behavioral events) or duration, measured in seconds (behavioral states), of all behaviors displayed by the animal focal during each treatment, using the BORIS 7.13 software (Friard and Gamba 2016). We classified the behaviors by comparing its motor pattern with an ethogram of the species (GSS unpublished data). Once our interest was to compare the display of displacement activities and aggressive behavior in the acoustic and visual treatments, we performed the statistical analysis only with non-rare behaviors that we classified as “displacement behavior” or “aggressive behavior” (Table 1; The theory and analysis to behavior classification is described in the supplementary material). To test our hypothesis that the emissions of aggressive and displaced behaviors would increase in treatments in which signal are partially degraded (25% of overlap with white noise), we conducted a Two Way Permutational Analysis of Variance (Frossard and Renaud 2021), using behavioral parameters (frequency or duration) as the response variable, acoustic (five levels: negative control, slightly degraded, moderate degraded, heavily degraded, positive control) or visual (three levels: clear, partial obstructed, obstructed) treatments and sex (two levels: female, male) as the predictors variables, and individuals as a random effect (repeated measures design).

We analyzed the audio recordings using Raven Pro 1.6 software (Cornell Laboratory of Ornithology Bioacoustics Research Program). From each call emission, we collected the following parameters: repetition rate (events/minute), number of notes (and/or pulses) per call, peak frequency (Hz), frequency (Hz) at 25% and at 75% of the call entropy and frequency of overlapping of acoustic signals and acoustic model signals (playback) (number of overlapping calls/total number of emitted calls, measured only for treatments with acoustic reproduction). To test if the vocalizations were altered by signal quality loss, we used general linear mixed models (GLMM). The data of calls frequencies (Hz) were adjusted with gamma family link inverse distribution, whether repetition rate and frequency of overlapping were adjusted with negative binomial distribution. Only the short vocalizations (calls) during the acoustic experiment were analyzed because long vocalizations (songs) were rare in both experiments and calls, although not rare in visual experiment, were displayed only a few times by each subject, resulting in a low sample size for some treatments.

Statistical analyzes were made in RStudio (R Core Team, 2021), using “dplyr” (Wickham et Al. 2021), “vegan” (Oksanen et al. 2020), “Factoshiny” (Vaissie et al. 2021), “Permuco” (Frossard and Renaud 2022), “lme4” (Bates et al. 2015), “car” (Fox et al. 2019) and “visreg” (Breheny and Burchett 2020) packages.

Following the best practices of p-value use and report proposed by Wasserstein (2016), we interpreted p-value as a continuous variable instead of a binary one with a threshold of p < 0.05 (principle 3 of the ASA statement on p-value, Wasserstein 2016). For that, we interpreted our p values as an indicator of the incompatibility of our data to the statistical model (Principle 1 of the ASA statement on p-value, Wasserstein 2016) and we considered that our data could provide different levels of support to our hypothesis (Principle 2 of the ASA statement on p-value, Wasserstein 2016), considering that: p < 0.1 denotes a weak support (trend), p < 0.05 denotes a moderate support, and p < 0.01 denotes a strong support.

Acoustic experiment

The birds did not change the rate of behaviors displayed during the acoustic experiment, except for the “Bill opening” behavior (PermANOVA: F_72,4=2.48, p=0.05), with greater rate of display in the positive control (Table 2, Figure 2). The interaction between information degradation and sex affected all acoustic parameters (Peak frequency, frequency at 75%, and at 25% of entropy) of the calls emitted by Sporophila maximiliani (Table 3, Figure 3). The frequency at 75% and at 25% of entropy calls emitted by males during positive control were lower than frequencies of vocalization during the other treatments (GLMM: p<0.01 and p=0.02, respectively). Moreover, the frequency at 25% of entropy and the peak frequency of males' calls were greater in heavy degradation (50% of information) of the signal treatment (GLMM: p<0.01 and p=0.02, respectively). Females did not present a difference in its calls between treatments (Figure 3). We did not found differences for call emission rate (GLMM: Treatment: p=0.39; Treatment*Sex: p=0.87; Sex: p=0.77) and frequency of overlapping of calls (GLMM: Treatment: p=0.99; Treatment*Sex: p=0.57; Sex: p=0.25) caused by treatments, sex or their interaction.

Visual communication

The birds did not change the rate of behaviors display in response to the quantity of visual information or sex, with the exception of “Feather settling” behavior (PermANOVA: F_36,2=3.2, p=0.05) and “Vigilance” behavior (PermANOVA: F_36,2=3.45, p=0.04), that were higher in the clear and partial obstructed treatments (Figure 4).

Our hypotheses were partially confirmed by our experiments. While signal interference induced modulation in the behavior and physical properties of the call of S. maximiliani, aggressiveness was not a preferential coping strategy. Moreover, the effects of signal interference were stronger in acoustic than visual signals, suggesting that signal modalities could play different roles during the communication of the Great-Billed Seed-Finch.

Response to complete and incomplete acoustic signaling

In the Acoustic experiment, the Great-Billed Seed-Finch increases the display of the “Bill opening” behavior in the treatment where the white noise totally masked the call model (no information available). This behavior is considered a maintenance behavior, because it has a regulatory function in the physiology and welfare of birds, helping the individual in thermoregulation (“Bill opening”) (Neto et al. 2021; Ferreira et al. 2022). The increase of this behavior is indicative of the bird anxiety (Neto et al. 2021), but was elicited by an unrecognized sound (the white noise) instead of the incompleteness of the information, suggesting a type of neophobia. The white noise, as an indecipherable sound, provides a stimulus that elicits a state of confusion about how to react to this stimulus, that is, a motivational conflict. There are evidence that birds can negatively react to artificial noise, producing an anxiety state and eliciting behavioral changes (Blesdoe and Blumstein 2014; Senar et al. 2017). So, the “Bill opening” would be a release behavior (i.e., displacement activity) elicited in response to the motivational conflict generated by the exposition of an unfamiliar stimulus. Other maintenance behaviors have already been registered as displacement activity for different bird species (Tinbergen 1952; Delius 1988; Dawkins et al. 1991), although we presented the first evidence of a thermoregulatory behavior as a displacement activity in birds.

We also found that birds emitted calls with lower frequency also in the treatment where the white noise totally masked the call model. Through their vocalizations, birds communicate aggression with low-frequency calls and fear or appeasement with higher-pitched sounds (Morton 2000). So, while white noise elicited the “Bill opening” behavior as a displacement activity, birds used aggressiveness as a coping strategy to an unknown acoustic stimulus. On the other hand, when exposed to incomplete information (heavily degraded treatments), calls of S. maximiliani males become higher-pitched, which suggest that individuals experienced fear (Morton 2000). Although the modulation of calls to higher tones, especially by increasing the minimum frequency, indicates a response to noise masking in birds (Warren et al. 2016), individuals cannot overcome the masking effect of the wideband noise in our experiment by shifting their calls’ spectral properties, as the white noise equally masks all frequency bands. Furthermore, the modulation in the call pitch does not occur in all treatments compared to the negative control, what would be expected if change in call tones were a strategy to cope with noise masking. The response of individuals to the heavily degraded experiment was not similar to the response to the positive control, and is caused by the noise interference in the acoustic signal, which impair the information interpretation and decision making. This stimulus triggers a behavioral path mediated by the motivational conflict state, but results in the display of a fear response instead of aggressiveness as we expected. Thus, we demonstrated that Great-Billed Seed-Finch react with an increase in aggressive motivation when submitted to an unrecognizable stimulus (neophobia elicited by the white noise) and with an increase in fear motivation when exposed to the heavily degraded treatment (incomplete information).

Fear and aggression are related to the same active-reactive personality axis (Push et al. 2018). In experiments performed in free range bird populations, new stimuli could elicit both fear and aggressiveness (Senar et al. 2017), although it is not clear what ecological traits select which coping strategies to display. Moreover, signal interference could elicit a fear response (our work) or aggressiveness (Furtado and Nomura 2014) as a coping strategy. We believe it is necessary to investigate other species' behavior in context of interference in information, to improve our understanding about the selection of birds' coping strategies.

Response to complete and incomplete visual signaling

We also found differences in the behavioral display of the Great-Billed Seed-Finch elicited by the incompleteness of visual information. In the complete obstructed signal treatment, vigilance was reduced, as none information of a potential competitor was available and no clue of imminent danger was perceived (Sapolsky et al. 2000). Conversely, in the treatments where the competitor's visual signals were available (the clear and partial obstructed signal), the focal animals spent more time vigilant, as an effort to gather additional data about the competitor condition and strength and to cope with the possibility of territory dispute (Tarjuelo et al. 2015). However, as we did not perceive any variation in vigilance between treatments that simulates the competitor’s complete or incomplete visual signaling, it seems that the interference in the visual signal did not change the coping strategy and did not elicit a variation in aggressive or fear motivation, as occurred in the acoustic context. When exposed to visual stimulus, the Great-Billed Seed-Finch search for more cues and avoids the emission of behaviors that have a higher energy cost, as aggressive behavior, without having sufficient information of the context (Shuhama et al. 2007; Samia et al. 2013), as well about the quality and condition of its competitor (Morton 2000).

Additionally, there was a higher display rate of “Feather settling” behavior in treatments with complete or incomplete information when compared to the treatment with no information of the competitor. Considering that Great-Billed Seed-Finch displayed also more vigilance in these treatments, it is probable that the emission of “Feather settling” in this context was a displacement activity, due the anxiety elicited by a potential competitor, as was already observer before for other bird species (Dawkins et al. 1991). However, partial information did not change the rate of display of displacement activities, and also did not mitigate or exacerbate the motivational conflict. Displacement activities can be evolutionary coopted and become true signals by the ritualization process, which reduces the motivational conflict by acquiring the secondary function of eliciting a response in other individuals (Tinbergen 1952; Krebs and Davies 1993). This process is generally used to explain the evolution of preening exhibition during courtship in duck species and the behavior of pecks on the ground by domestic cocks during fighting (Dawkins et al. 1991).

The modulation of the behavioral response of the Great-Billed Seed-Finch was dependent on the signal modality. Visual information elicits a pre-aggressive state of vigilance in individuals, while acoustic information generates lesser vigilance response. Also, increased interference in acoustic signals resulted in fear, and an unrecognized noise provoked aggressiveness. Sporophila maximiliani exhibits little variation on plumage coloration, body size and bill shape throughout its geographical range (Ubaid et al. 2018), but it has a large variation in call and song types, accentuated by the domestication process (Marques 2009). While variation in acoustic signals could reduce the aggressive disposition, individuals would require more samples of the signal to compare to its own call and evaluate whether the sender is a potential competitor or not (Ubaid et al. 2018). So, the visual information would generate less ambiguity, as morphology is less variable, and result in stronger behavioral responses, even when few competitor’s samples were available.

Probably other factors that we have not evaluated may affect the response of individuals to signal interference. One such factor is variation in call structure (dialects), which could increase the amount of information necessary to a proper context evaluation, or habituation, as supported by the dear enemy hypothesis (Fisher 1954), that could lessen aggression toward familiar individuals. Therefore, we encourage further studies with other passerine species to expand our understanding of behavioral responses under information loss conditions and to identify the broader consequences of signal degradation for birds. Moreover, the vocal modulation observed in S. maximiliani suggests a sensitivity to changes in their soundscape, once environmental noise may negatively affect their fitness (Seyfarth et al. 2010; Vielliard and Silva 2010). Given its endangered status and potential for reintroduction in the wild, understanding the conditions that elicit and control this call modulation is crucial. Future studies should investigate how noise levels, types, and other contextual factors influence call frequency modulation to assess the Great-Billed Seed-Finch’s sensitivity and resilience to anthropic noise.

Acknowledgments

We thank the Centro de Triagem de Animais Silvestres de Goiás (CETAS-GO) for supply the animals and give the logistical support in the experiments. We also thank the Associação Floresta Cheia Instituto de Conservação Ambiental for the partnership in the development of Bicudos do Cerrado project.

Funding

This work was supported by the Fundação de Amparo à Pesquisa do Estado de Goiás (grant number 202110267000403).

Statements and Declarations

Ethics Approval: The use of animals in our experimentations was approved by the Ethics Committee on the Use of Animals in Experiments from the Universidade Federal de Goiás (CEUA/UFG, protocol 077/21).

Competing Interests: All authors declare no competing interests.

Data Availability Statement

The data underlying this article are available in the Zenodo repository (https://doi.org/10.5281/zenodo.10428308).

Significance Statement

The interference in signal quality during animal communication may affect the interpretation of information and, consequently, can affect the behavioral response of individuals. Signal interference can increase the ambiguity of the interaction, as incomplete information impairs the capacity of the receiver to evaluate the sender’s motivation and status. In this article, we present evidence from experiments that the loss of acoustic information caused by background noise elicits fear responses in males of the Great-Billed Seed-Finch, Sporophila maximiliani. Therefore, information uncertainty acts as a stressor. However, visual signals do not elicit the same responses, once both complete or incomplete information elicit displacement activities. Thus, visual information may be less ambiguous than acoustic information for this species. Understanding these processes can increase the knowledge of birds in noise environments and contribute to their conservation.

Author contributions

Gabriela Sales dos Santos and Fausto Nomura contributed to the conceptualization and the designing of the methodology. Gabriela Sales dos Santos and Lara Louredo Leal made the data collection. Gabriela Sales dos Santos performed the data analysis and writing - original draft. Fausto Nomura supervised. All authors contributed to the writing - review and editing and approved the final manuscript.

Audacity Team (2021) Audacity(R): Free Audio Editor and Recorder [Computer application]. Version 3.0.2. Accessed in: : https://www.audacityteam.org/.
Akçay Ç, Wood WE, Searcy WA, Templeton CN, Campbell SE, Beecher MD (2009) Good neighbour, bad neighbour: song sparrows retaliate against aggressive rivals. Anim. Behav. 78(1):97–102. https://doi.org/10.1016/j.anbehav.2009.03.023.
Anderson MJ (2001a) A new method for non-parametric multivariate analysis of variance. Austral Ecol. 26, 32–46. https://doi.org/10.1111/j.1442-9993.2001.01070.pp.x.
Bates D, Mächler M, Bolker B, Walker S (2015) Fitting Linear Mixed-Effects Models Using lme4. J Stat Soft 67(1):1-48. https://doi.org/10.18637/jss.v067.i01.
Benus RF, Bohus B, Koolhaas JM, van Oortmerssen GA (1991) Heritable variation for aggression as a reflection of individual coping styles. Experientia. 47:1008-1019. https://doi.org/10.1007/bf01923336.
BirdLife International (2019) Sporophila maximiliani (amended version of 2017 assessment). The IUCN Red List of Threatened Species 2019: e.T22723537A155473409.https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T22723537A155473409.en. Downloaded on 14 September 2022.
Blesdoe EK, Blumstein DT (2014) What is the sound of fear? Behavioral responses of white-crowned sparrows Zonotrichia leucophrys to synthesized nonlinear acoustic phenomena. Current Zoology 60:534–541. https://doi.org/10.1093/czoolo/60.4.534.
Bolhuis JE, Schouten WGP, Schrama JW, Wiegant M (2005) Individual coping characteristics, aggressiveness and fighting strategies in pigs. Anim. Behav. 69:1085-1091. https://doi.org/doi:10.1016/j.anbehav.2004.09.01.
Breheny P, Burchett W (2020) visreg: Visualization of Regression Models. R Packages version 2.7.0. Accessed in: https://cran.r-project.org/web/packages/visreg/index.html.
Brumm H, Todt D (2002) Noise-dependent song amplitude regulation in a territorial songbird. Anim. Behav. 63:891-897. https://doi.org/doi:10.1006/anbe.2001.1968.
Brumm H, Todt D (2004) Male-male vocal interactions and the adjustment of song amplitude in a territorial bird. Anim. Behav. 67:281-286. https://doi.org/doi:10.1016/j.anbehav.2003.06.006.
Choi EA, Husić M, Millan EZ, Gilchrist S, Power JM, dit Bressel PJR, McNally GP (2022) A Corticothalamic Circuit Trades off Speed for Safety during Decision-Making under Motivational Conflict. J Neurosci. 42(16):3473–3483. https://doi.org/10.1523/JNEUROSCI.0088-22.2022.
Curry CM, Antze B, Warrington MH, Brisay PD, Rosa P, Koper N (2018) Ability to alter song in two grassland songbirds exposed to simulated anthropogenic noise is not related to pre-existing variability. Bioacoustics. 27(2):105-130. https://doi.org/10.1080/09524622.2017.1289123.
Cynx J, Lewis R, Tavel B, Tse H (1998) Amplitude regulation of vocalizations in noise by a songbird, Taeniopygia guttata. Anim. Behav. 56:107–113. https://doi.org/10.1006/anbe.1998.0746.
Dawkins MS, Halliday TR, Dawkins R (1991) The Tinbergen legacy. Chapman and Hall, London.
Delius JD (1988) Preening and Associated Comfort Behavior in Birds. Ann. N. Y. Acad. Sci. 525:40-55. https://doi.org/10.1111/j.1749-6632.1988.tb38594.x.
Falk JL (1977) The origin and function of adjunctive behavior. Anim. learn. behav. 5 (4):325-335. https://doi.org/10.3758/BF03209574.
Ferreira JA, Valentim JK, Machado LC, Oliveira HF (2022) Elaboração de etograma para poedeiras criadas em gaiolas. Rev. Ciênc. Agron. 21(2):135-147. https://doi.org/10.5965/223811712122022137.
Fisher J, Huxley J, Hardy AC, Ford EB (1954) Evolution and bird sociality, Evolution as a process, LondonAllen & Unwin.
Font E, Carazo P (2010) Animals in translation: why there is meaning (but probably no message) in animal communication. Anim. Behav. e1-e6. https://doi.org/10.1016/j.anbehav.2010.05.015.
Fox J, Weisberg S, Price B, Adler D, Bates D, Baud-Bovy G, Bolker S, Ellison S, Firth D, Friendly M, et al. (2019) car: Companion to Applied Regression. R Package version 3.1-2. Accessed in: https://cran.r-project.org/web/packages/car/index.html.
Friard O, Gamba M (2016) BORIS: a free, versatile open-source event-logging software for video/audio coding and live observations. Methods Ecol. Evol. 7:1325-1330. https://doi.org/10.1111/2041-210X.12584.
Frohlich M, Sievers C, Townsend WS, Gruber T, Van Schaik CP (2019) Multimodal communication and language origins: integrating gestures and vocalizations. Biol. Rev. 94: 1809–1829. https://doi.org/10.1111/brv.12535.
Frossard J, Renaud O (2021) Permutation Tests for Regression, ANOVA, and Comparison of Signals: The permuco Package. J Stat Soft 99(15). https://doi.org/10.18637/jss.v099.i15.
Furtado R, Nomura F (2014) Visual signals or displacement activities? The function of visual displays in agonistic interactions in nocturnal tree frogs. Acta Ethol. 17:9-14. https://doi.org/10.1007/s10211-013-0160-6.
Gerhardt HC (1992) Multiple messages in acoustic signals. The Neurosciences. 4:391-400. https://doi.org/10.1016/1044-5765(92)90047-6.
Giasson LOM, Haddad CFB (2006) Social interactions in Hypsiboas albomarginatus (Anura: Hylidae) and the significance of acoustic and visual signals. J. Herpetol. 40:171-180. http://dx.doi.org/10.1670/205-05A.1.
Grabarczyk EE, Grill AS (2019) Anthropogenic noise affects male house wren response to but not detection of territorial intruders. PLoS ONE. 14(7):e0220576. https://doi.org/10.1371/journal.pone.0220576.
Grabarczyk EE, Gill AS (2020) Anthropogenic noise masking diminishes house wren (Troglodytes aedon) song transmission in urban natural areas. Bioacoustics. 29(5):518-532.
Grabarczyk EE, Vonhof MJ, Gill AS (2020) Social context and noise affect within and
between male song adjustments in a common passerine. Behav. Ecol. 31(5):1150-1158. https://doi.org/10.1093/beheco/araa066.
Grade Q, Sieving KE (2016) When the birds go unheard: highway noise disrupts information transfer between bird species. Biol. Lett.12:20160113. http://dx.doi.org/10.1098/rsbl.2016.0113.
Halfwerk W, Slabbekoorn H (2009) A behavioural mechanism explaining noise-dependent frequency use in urban birdsong. Anim. Behav. 78(6):1301–1307. https://doi.org/10.1016/j.anbehav.2009.09.015.
Hansen, IJK, Otter KA, Oort H, Holschuh CI (2005) Communication breakdown? Habitat influences on black-capped chickadee dawn choruses. Acta Ethol. 8(2): 111-120. https://doi.org/10.1007/s10211-005-0007-x.
Hartmann MT, Giasson LOM, Hartmann PA, Haddad CFB (2005) Visual communication in Brazilian species of anurans from the Atlantic Forest. J. Nat. Hist. 39(19):1675-1685. http://dx.doi.org/10.1080/00222930400008744.
Herculano DM, Santos MAB, Pigozzo CM (2013) Etograma de Flamingo-Chileno, Phoenicopterus Chilensis (phoenicopteriformes, phoenicopteridae), em condição de cativeiro no Parque Zoobotânico Getúlio Vargas. Candombá. 9(1):8-21.
Hof D, Hazlett N (2010) Low-amplitude song predicts attack in a North American wood warbler. Anim. Behav. 80:821-828. https://doi.org/10.1016/j.anbehav.2010.07.017.
ICMBIO (2018) Livro vermelho da fauna brasileira ameaçada de extinção: Volume I. 1. ed. Brasília - DF: ICMBio/ Ministério do Meio Ambiente.
Jolliffe IT (2002) Principal Component Analysis. Springer, New York.
Koolhaas JM, Korte SM, De Boer SF, Van Der Vegt BJ, Van Reenen CG, Hopster H, De Jong IC, Ruis MAW, Blokhuis HJ (1999) Coping styles in animals: current status in behavior and stress-physiology. Neurosci. Biobehav. Rev. 23:925-935.
Kraft FL, Forštová T, Utku Urhan A, Exnerová A, Brodin A (2017) No evidence for self-recognition in a small passerine, the great tit (Parus major) judged from the mark/mirror test. Anim Cogn. 20(6):1049–1057. https://doi.org/10.1016/s0149-7634(99)00026-3.
Krebs JR, Davies NB (1993) An introduction to behavioural ecology. Blackwell Publishing, Oxford.
Leitão A V., Hall ML, Delhey K, Mulder RA (2019) Female and male plumage colour signals aggression in a dichromatic tropical songbird. Anim Behav. 150:285–301. https://doi.org/10.1016/j.anbehav.2019.01.025.
Lenis PR, Ferreira RG (2020) Effect of noise on behavioural response to simulated territorial intrusion in the Great Kiskadee (Pitangus sulphuratus) (Aves: Tyrannidae). Urban Ecosystems. 23:93-96. https://doi.org/10.1007/s11252-019-00906-1.
Lin Y, Ma J, Zhao J, Liu Q, Pei E, Zhang E, Chen M (2021) Mirror responses in the common hill myna (Gracula religiosa) and the African grey parrot (Psittacus erithacus). Zoology. 147:125942. https://doi.org/10.1016/j.zool.2021.125942.
Lombard E (1911) Le signe de l’elevation de la voix. Annales des Maladies de L'Oreille et du Larynx. 37:101-119.
Lovell SF, Lein MR (2004) Neighbor-stranger discrimination by song in a suboscine bird, the alder flycatcher, Empidonax alnorum. Behav. Ecol. 15(5):799–804. https://doi.org/10.1093/beheco/arh082.
Luther DA, Phillips J, Derryberry EP (2016) Not so sexy in the city: urban birds adjust
songs to noise but compromise vocal performance. Behav. Ecol. 27(1):332-340. https://doi.org/10.1093/beheco/arv162.
Machado RB, Silveira LF, Silva MISG, Ubaid FK, Medolago CA, Francisco MR, Dianese JC (2020) Reintroduction of songbirds from captivity: the case of the Great‐billed Seed‐fnch (Sporophila maximiliani) in Brazil. Biodivers. Conserv. 29:1613-1636. https://doi.org/10.1007/s10531-019-01830-8.
Maestripieri D, Schino G, Aurelis F, Troisi A (1992) A modest proposal: displacement activities as an indicator of emotions in primates. Anim. Behav. 44:967-979. https://doi.org/10.1016/S0003-3472(05)80592-5.
Marler P (1957) Specific Distinctiveness in the communication signals of birds. Behaviour. 11(1):13-39. https://doi.org/10.1163/156853956X00066.
Marques, AB (2008) Abordagens sobre a bioacústica na ornitologia Parte I - Conceitos básicos. Atual. Ornitol. (146):38-40.
Marques AB (2009) Abordagens sobre a bioacústica na ornitologia Parte II - Bioacústica relacionada com outros campos do conhecimento. Atual. Ornitol. 147(147):33-5.
Maynard-Smith J, Harper D (2003) Animal Signals. Oxford Series on Ecology and Evolution. Oxford University Press, Oxford.
McGregor PK, Catchpole CK, Dabelsteen T (1992) Design of playback experiments: the Thornbridge Hall NATO ARW consensus. In: McGregor PK editor. Playback and studies of animal communication. 1st ed. Springer, New York. pp. 1–9.
Medolago CAB, Ubaid FK, Francisco MR, Silveira LF (2016) Description of the nest and eggs of the Great-billed Seed-Finch (Sporophila maximiliani). Wilson J. Ornithol. 128(3):638-642. http://dx.doi.org/10.1676/1559-4491-128.3.638.
Morton ES (1977) On the occurrence and significance of motivation-structural rules in some bird and mammal sounds. Am. Nat. 111(981):855-869.
Morton ES (2000) An evolutionary view of the origins and functions of avian vocal communication. Jap. J. Ornithol. 49:69-78. https://doi.org/10.3838/jjo.49.69.
Møller AP, Pomiankowski A (1993) Why have birds got multiple sexual ornaments? Behav. Ecol. Sociobiol. 32:167-176. https://doi.org/10.1007/BF00173774.
Nemeth E, Brumm H (2010) Birds and Anthropogenic Noise: Are Urban Songs Adaptive? Am. Nat. 176(4)465-475. https://doi.org/10.1086/656275.
Nemeth E, Pieretti N, Zollinger SA, Geberzahn N, Partecke J, Mirand AC, Brumm H (2013) Bird song and anthropogenic noise: Vocal constraints may explain why birds sing higher-frequency songs in cities. Proc R Soc B Biol Sci. 280(1754):1–7. https://doi.org/10.1098/rspb.2012.2798.
Neto GSF, Prado MA, Neves PUC, Oliveira RG, Guimarães EF (2021) Comparação da diversidade de comportamentos exibidos por emas em cativeiro e recém liberadas. Pesqui. Ensino Ciênc. Exatas Nat.. 5:1809. http://dx.doi.org/10.29215/pecen.v5i0.1809.
Oksanen J et al (2020) vegan: Community Ecology Package. R package version 2.5-7. Accessed in: https://cran.r-project.org/package=vegan.
Onsal C, Yelimlies A, Akçay C (2022) Aggression and multi-modal signaling in noise in a common urban songbird. Behav. Ecol. Sociobiol. 76(7):102. https://doi.org/10.1101/2022.04.29.490020.
Osorio D, Vorobyev M (2008) A review of the evolution of animal colour vision and visual communication signals. Vis. Res. 48:2042-2051. https://doi.org/10.1016/j.visres.2008.06.018.
R Core Team (2021) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Accessed in: https://www.R-project.org/.
Pereira DF, Batista ES, Sanches FT, Filho LRAG, Bueno LGF (2015) Diferenças comportamentais de poedeiras em diferentes ambientes térmicos. Energ. na agric. 30(1): 33-40. https://doi.org/10.17224/EnergAgric.2015v30n1p33-40.
Porto GR, Pitarelli A (2005) Etograma da maria-preta, Molothrus bonariensis (Gmelin) (Aves, Emberizidae, Icterinae). Rev. Bras. Zool. 22(2):306-312. https://doi.org/10.1590/S0101-81752005000200002.
Pusch EA, Bentz AB, Becker DJ, Navara KJ (2018) Behavioral phenotype predicts physiological responses to chronic stress in proactive and reactive birds. General and Comparative Endocrinology 255:71–77. https://doi.org/10.1016/j.ygcen.2017.10.008.
Samia DSM, Nomura F, Blumstein DT (2013) Do animals generally flush early and avoid the rush? A meta-analysis. Biol. Lett. 9:1-4. http://dx.doi.org/10.1098/rsbl.2013.0016.
Santarém, EMM, Silva, MTA (1999) Comportamento adjunto: controvérsias e contribuições teóricas. Psicol.: Teor. Pesqui. 15:199-207. https://doi.org/10.1590/S0102-37721999000300003.
Sapolsky RM, Romero LM, Munck AU (2000) How do glucocorticoids influence stress responses? Integrating permissive, suppressive, stimulatory, and preparative actions. Endocr. Rev. 21(1):55–89. https://doi.org/10.1210/edrv.21.1.0389.
Sebeok TA (1968) Animal communication: techniques of study and results of research. Indiana University Press, Boomington.
Seyfarth RM, Cheney DL, Bergman T, Fischer J, Zuberbühler K, Hammerschmidt K (2010) The central importance of information in studies of animal communication. Anim. Behav. 80:3-8. https://doi.org/10.1016/j.anbehav.2010.04.012.
Shuhama R, Del-Ben CM, Loureiro SR, Graeff FG (2007) Animal defense strategies and anxiety disorders. An Acad Bras Cienc. 79(1):97–109. https://doi.org/10.1590/s0001-37652007000100012.
Silva ML, Vielliard JME (2011) A aprendizagem vocal em aves: evidências comportamentais e neurobiológicas. In: Henriques AL, Assis GJA, Brito RCS, Martin WLB editors. Estudos do comportamento II. Editora da UFPA, Belém, pp. 177-197.
[dataset] Silva RS, Lima B (2009) Bicudo-verdadeiro (Sporophila maximiliani), Xeno-canto, XC39102.
Smith CL, Taylor A, Evans CS (2011) Tactical multimodal signaling in birds: facultative variation in signal modality reveals sensitivity to social costs. Anim. Behav. 82: 521-527. https://doi.org/10.1016/j.anbehav.2011.06.002.
Smith O, Wassmer T (2016) An ethogram of commonly observed behaviors of the endangered Bridled White-eye (Zosterops conspicillatus) in a Zoo Setting. Wilson J. Ornithol. 128(3):647-653. https://doi.org/10.1676/1559-4491-128.3.647.
Smith WJ (1977) The behavior of communicating: an ethological approach. Harvard University Press, Cambridge.
Starnberger I, Preininger D, Hödl W (2014) From uni‐ to multimodality: towards an integrative view on anuran communication. J. Comp. Physiol. A. 200:777–787. https://doi.org/10.1007/s00359-014-0923-1.
Steimer T 2002 The biology of fear- and anxiety-related behaviors. Dialogues Clin. Neurosci. 4:231-249. https://doi.org/10.31887/DCNS.2002.4.3/tsteimer.
Tarjuelo R, Barja I, Morales MB, et al (2015) Effects of human activity on physiological and behavioral responses of an endangered steppe bird. Behavioral Ecology 26:828–838. https://doi.org/10.1093/beheco/arv016.
Tinbergen N (1952) “Derived” activities; their causation, biological significance, origin, and emancipation during evolution. Q. Rev. Biol. 27:1–32.
Trajano MC, Carneiro LP (2019) Diagnóstico da criação comercial de animais silvestres no Brasil. Ibama, Brasília.
Ubaid FK, Silveira LF, Medolago CBA, Costa TVV, Francisco MR, Barbosa KVC, Juior ADS (2018) Taxonomy, natural history, and conservation of the Great-billed Seed-Finch Sporophila maximiliani (Cabanis, 1851) (Thraupidae, Sporophilinae). Zootaxa. 4442(4): 551-571. https://doi.org/10.11646/zootaxa.4442.4.4.
Ubaid FK, Malacco GB, Medolago CAB, Silveira LF (2021) Reintroduction of the great-billed seed-finch in the Brazilian Cerrado, Brazil. In: Soorae PS, editor. Global Conservation Translocation Perspectives. 7th ed. IUCN SSC Conservation Translocation Specialist Group, Canada, pp. 148-151.
Vaissie P, Monge A, Husson F (2021) Factoshiny: Perform Factorial Analysis from 'FactoMineR' with a Shiny Application. R package version 2.4. Disponível em: https://cran.r-project.org/web/packages/Factoshiny/index.html.
Velásquez NA, Moreno-Gómez FN, Brunetti E, Penna M (2018) The acoustic adaptation hypothesis in a widely distributed South American frog: Southernmost signals propagate better. Sci Rep. 8(1):1–12. https://doi.org/10.1038/s41598-018-25359-y.
Vielliard JME, Silva ML (2010) Bioacústica - bases teóricas e regras práticas de uso em ornitologia. In: Matter SV, Piacentini VQ, Straube FC, Cândido JF, Accordi IA. Ornitologia e conservação: ciência aplicada, técnicas de pesquisa e levantamento. 1st ed. Technical Books, Rio de Janeiro, pp. 313-326.
Villain AS, Fernandez MSA, Bouchut C, Soula HA, Vignal C (2016) Songbird mates change their call structure and intrapair communication at the nest in response to environmental noise. Anim. Behav. 116:113–129. https://doi.org/10.1016/j.anbehav.2016.03.009.
Warren, PS, Katti M, Ermann, M, Brazel, A (2006) Urban bioacoustics: it’s not just noise. Anim. Behav. 71:491-502. https://doi.org/10.1016/j.anbehav.2005.07.014.
Wasserstein RI (2016) ASA statement on statistical significance and P-values. Am. Stat. 70(2):129-133.
Wickham H, Girlich M, Ruiz E (2021) dplyr: A’dplyr’Back End for Databases. R package version 2.1.1. Accessed in: https://cran.r-project.org/package=dplyr.
Zeigler HP (1964) Displacement activity and motivational theory: a case study in the history of ethology. Psychol. Bull. 61(5):362-376. https://doi.org/10.1037/h0044307.
(2023)[bicudo (Sporophila maximiliani)]. WikiAves, a Enciclopédia das Aves do Brasil. Available in: <http://www.wikiaves.com.br/cantador-de-rondon>, Accessed in: 08/5/2023.

Table 1 Behaviors of Sporophila maximiliani displayed during acoustic and visual experiments that are aggressive signal or possible displacement activities and were analyzed in statistical tests.

Category	Classification	Behavior
Maintenance	Possible displacement activities	- Autopreening*
		- Bill cleaning
		- Bill opening
		- Feather settling
Locomotion	Possible displacement activities	- Jump between perches**
		- Flight
Ingestion/egestion	Possible displacement activities	- Eating
Alert	Pre-aggressive behavior	- Vigilance
		- Perch in the cage*
		- Jump on the perch changing orientation
		- Stretching neck

* Behavior that was analyzed only in acoustic experiment, since it did not present a great contribution to visual experiment behaviors variability or were rare.

** Behavior that was analyzed only in visual experiment, since it did not present a great contribution to acoustic experiment behaviors variability.

Table 2 p-Value of the permutational Anova tests proceed with behaviors tested in the acoustic and visual experiment. behaviors without value were not tested in one of the experiments (see supplementary material to understand the criteria of inclusion).

Behavior tested	p-Value (acoustic experiment)			p-Value (visual experiment)
Behavior tested	Treatment	Sex	Treatment:Sex	Treatment	Sex	Treatment:Sex
Autopreening	0.42	0.65	0.20	-	-	-
Bill cleaning	0.52	0.46	0.28	0.17	0.33	0.69
Bill opening	0.05	0.82	0.63	0.37	0.89	0.86
Feather settling	0.10	0.31	0.60	0.05	0.73	0.23
Flight	0.79	0.18	0.78	0.47	0.42	0.62
Jump between perches	-	-	-	0.97	0.57	0.82
Eating	0.84	0.26	0.89	0.28	0.56	0.37
Vigilance	0.72	0.09	0.96	0.04	0.14	0.26
Perch in the cage	0.33	0.32	088	-	-	-
Jump on the perch changing orientation	0.53	0.03	0.29	0.64	0.83	0.87
Stretching neck	0.56	0.17	0.44	0.13	0.50	0.478

Table 3. Anova of the linear mixed model adjusted to the acoustic parameters of calls.

	Frequency 75			Frequency 25			Peak Frequency
Predictors	Q	df	p-value	Q	df	p-value	Q	df	p-value
Treatment	3.78	4	0.42	5.32	4	0.26	6.87	4	0.14
Sex	2.28	1	0.13	3.34	1	0.07	1.87	1	0.17
Treatment:Sex	13.21	4	0.01	18.68	4	<0.001	9.19	4	0.06

01SuppBehavclass.docx

Communication breakdown! Signal modality drives the effect of information loss on the behavioral responses of the threatened Great-Billed Seed-Finch, Sporophila maximiliani (Thraupidae: Passeriformes)

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Abstract

Figures

Introduction

Methods

Results

Discussion

Conclusion

Declarations

References

Tables

Supplementary Files

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