Biology subjects

Akcay, C.

Publications and source records attributed to Akcay, C..

17 recordsLinked to original sources

bioRxiv2026

Sex-specific functions of duetting in the Galapagos Yellow Warbler (Setophaga petechia aureola)

In over a thousand avian species, pairs coordinate vocalizations to form duets. Songbirds may use calls (simple, non-learned vocalizations) and songs (complex, learned vocalizations) to answer their partners. In Galapagos Yellow Warblers (Setophaga petechia aureola), song answers in duets appear to have evolved recently in addition to older call answers. Here, we explored the structure and functions of duets in an observational study to understand why song answers in duets may have evolved. We first described the temporal structure of duets initiated by either sex. We then tested whether the distance between pair members, countersinging with neighbours, and timing relative to aggressive encounters predicted answering probability for each sex. Finally, we tested whether the behavioral context of call and song answers differed. We found that most duets were initiated by males, and call answers were almost exclusively given by females. Female answers were also more tightly coordinated than those of males. Female answering probability decreased with increasing distance between pair members, whereas male answering probability did not. In addition, females were less likely to answer with songs when farther from their mate. Females answering probability also increased slightly when their mates initiation was preceded by a neighbors song. Our results show some evidence in support of the joint resource defence hypothesis for female answers. On the other hand, the significance of song in female answers may be related to some other functions that we did not test here, such as signaling quality or commitment to the pair bond. Lay summaryWho turns a song into a duet? In Galapagos Yellow Warblers, it is usually the female: she answers her mates song with a tightly timed call or song. Male replies were rarer and less coordinated. While male replies didnt seem to have a function, female replies were used in territorial disputes with neighbours and may indicate joint ownership of a territory. Female song replies, on the other hand, may signal commitment to the pair bond.

animal behavior and cognition↗

bioRxiv2026

A comparison of BirdNET, expert listening and acoustic indices to monitor avian diversity in a Mediterranean agricultural landscape

Passive acoustic monitoring poses an immense potential to assess avian diversity in many habitats, including agricultural landscapes. At the same time, automated recorders generate large datasets which present a challenge for processing and effectively assessing biodiversity. Methods such as manual listening by experts, automated detection algorithms like BirdNET and calculating acoustic indices all present different trade-offs in assessment of biodiversity through passive acoustic monitoring. In the present study we recorded soundscapes in a low-intensity agricultural landscape in western Turkiye in all four seasons. Two expert ornithologists listened to a subset of these recordings identifying bird species from the recordings. We also ran the same sample of recordings on BirdNET to compare BirdNET detections with expert detections and calculated acoustic indices for each recording. The results showed that BirdNET detected more species than experts, although some may not be reliable detections. Two acoustic indices (bioacoustic index and acoustic complexity index) were correlated positively with number of species detected by experts and one (normalized difference soundscape index) with number of species detected by BirdNET but the correlations were modest. The results show that acoustic indices may have limited value in detecting biodiversity and automated detection algorithms may do a better job, although these may need to be trained with local data to improve detection and classification.

ecology↗

bioRxiv2025

Flexibility of territorial aggression in urban and rural Chaffinches

Rapid environmental change due to urbanization poses novel challenges to animals. Behavioral change and individual plasticity are generally hypothesized to be the key to adapting to these challenges. One commonly observed behavioral change is higher observed aggression levels in urban animals, perhaps because anthropogenic noise disrupts effective acoustic communication during conflicts, leading to greater use of physical aggression. We investigated the hypothesis that urban noise drives aggression by performing repeated simulated territorial intrusion experiments on rural and urban chaffinches (Fringilla coelebs). We expected urban chaffinches to be more aggressive, change their aggression levels more between trials, and for aggression to increase with noise levels, irrespective of the habitat. We found that while aggression didnt differ between habitats in the initial trial, rural chaffinches decreased their aggression level in the second trial and thus were less aggressive than the urban chaffinches, who did not change their response. That is, urban birds were less flexible in responding to an intruder than rural birds, contrary to previous findings in other songbirds. Moreover, there was an increase in aggression with increasing noise levels, irrespective of the habitat. Given our small sample size and lack of spatial replicates, our results should be interpreted with caution. Nevertheless, as a lack of flexibility in aggression is potentially costly, our results highlight the importance of studying the plasticity in aggressive behavior in human-impacted landscapes.

animal behavior and cognition↗

bioRxiv2025

Cultural and morphological divergence of Darwin's cactus finches (Geospiza scandens) across the Galapagos Islands

Understanding the divergence of cultural traits, such as bird song, provides critical insights into evolutionary processes. In geographically isolated populations, the divergence of traits associated with mate choice can lead to further genetic separation. This study investigates divergence in song syllable types, acoustic characteristics, singing behavior, and morphology in two allopatric populations of Darwins cactus finch (Geospiza scandens) on Floreana and Santa Cruz Islands in the Galapagos Archipelago. Using song recordings of 50 males, we identified 25 syllable types with no overlap between islands, indicating a complete divergence in syllable repertoires. Syllables of Floreana and Santa Cruz males diverged in the acoustic space largely due to broader frequency bandwidths on Floreana. Moreover, Floreana males had smaller beaks than Santa Cruz males. Despite acoustic and morphological divergence, singing behaviors - like syllable repetition rate and number of syllables per song - did not differ significantly. Both cultural processes, including drift and transmission biases, as well as selection on morphology could have contributed to the observed acoustic divergence. This study adds to a growing literature on the role of geographic separation in the accumulation of both cultural and morphological divergence between populations. Future research could interrogate speciation scenarios in cactus finches if populations cease to interbreed after secondary contact.

animal behavior and cognition↗

bioRxiv2025

Solo songs, duets, and territory defense across seasons in female Galapagos Yellow Warblers (Setophaga petechia aureola)

While the function of bird song has been well studied in male songbirds, the function of female song is less well understood. This is partly due to a historical view of females occupying a passive role compared with males, which led to ignoring female song even in some well-studied species. We report one such case in yellow warblers (Setophaga petechia), as no other study investigated female song in 35 years after the first documentation of solo female songs. We interrogate the seasonal patterns and functions of female song in Galapagos yellow warblers (Setophaga petechia aureola), in which females perform solo song and produce duets with their male social partners. We carried out simulated territory intrusions by broadcasting male, female, or duet songs during breeding and non-breeding seasons, and conducted a territory retention survey for over a year. We measured the association between aggressive response and singing behaviour, sex-specific patterns of response, and territory retention across years. Females sang mostly during the non-breeding season and predominantly in male-led duets. Although females were strongly aggressive towards female song playback, they gave the weakest singing response towards them. There was no association between female aggressive behaviour and song output in response to a simulated intruder. Moreover, the probability of territory retention across years was not explained by song output or aggression in response to intruders, though evidence for this was weak due to the small sample size. We suggest that female song in this year-round resident island system does not function for territory defense or intrasexual competition, but may have other functions. HighlightsO_LIGalapagos Yellow Warbler females produce solo songs and duets with their male partners. C_LIO_LIFemale song and aggression were mainly restricted to the non-breeding season. C_LIO_LIWhile females were equally aggressive to all intruders, they had the lowest song rate in response to females. C_LIO_LIIn contrast to males, aggressive behaviour didnt predict song output in females. C_LIO_LIFemale singing behaviour did not increase the probability of territory retention. C_LI

animal behavior and cognition↗

bioRxiv2024

Galapagos yellow warblers in low- and high-traffic environments differ in song plasticity in response to noise.

Acoustic communication between animals is increasingly disrupted by noise in human-altered environments making signals less effective. Birdsong is a signal used in agonistic interactions between territorial rivals, and birds may modify their song and singing behaviour in response to noise. However, if these modifications are still ineffective, this can lead to increased conflict between rivals. Here, we asked whether experimental traffic noise induces immediate changes in acoustic characteristics of song and aggressive behaviour in populations and territories that differ greatly in traffic noise exposure. We conducted simulated territorial intrusions on Galapagos yellow warblers (Setophaga petechia aureola) living on Santa Cruz (high traffic) and Floreana (low traffic) islands. Territories were either adjacent to the nearest road or at least 100 m away from it. We assessed the focal birds physical response levels and recorded their vocalisations in response to playback of conspecific song (control) and conspecific song coupled with traffic noise (noise treatment). We found that physical response levels mostly depended on treatment and distance to the nearest road: on both islands, birds living adjacent to the nearest road increased their aggression levels with experimental noise compared to control, while birds living farther away decreased their aggression levels. Birds on all islands irrespective of their distance to a road increased minimum frequency of their songs during the noise treatment. However, change in peak frequency and duration of their songs depended on the habitat they live in. Our results suggest behavioural flexibility in territorial responses and birdsong in response to traffic noise, which appears to depend at least in part on prior experience with traffic noise. HighlightsO_LIGalapagos yellow warblers modified their behaviour in response to traffic noise. C_LIO_LIBehavioural plasticity depended on the island and distance to the nearest road. C_LIO_LIBirds living close to a road increased their aggression in response to an intruder C_LIO_LIBirds living farther away from a road decreased their aggression. C_LI

animal behavior and cognition↗

bioRxiv2022

Terminal flourishes but not trills differ between urban and rural chaffinch song

Anthropogenic noise interrupts the acoustic communication between animals living in urban habitats. Accumulating evidence suggests that animals can evade this interruption using various strategies such as shifting frequencies upwards or increasing the duration of their signals. In this study, we compared the time and frequency-related characteristics of songs and rain calls of common chaffinches (Fringilla coelebs) inhabiting rural forests and an urban park in Turkey. Most of the song phrases and rain calls did not differ in any of the characteristics measured between urban and rural chaffinches. Terminal flourish phrases of the songs, however, had lower minimum frequencies and broader bandwidth in urban territories, contrary to our predictions. We discuss this finding in relation to its potential adaptive significance.

animal behavior and cognition↗

bioRxiv2022

Aggression and multimodal signaling in noise in the European robin

Anthropogenic noise may disrupt signals used to mediate aggressive interactions, leading to more physical aggression between opponents. One solution to this problem is to switch signaling effort to a less noisy modality (e.g., the visual modality). In the present study we investigate aggressive behaviors and signaling in urban and rural male European robins (Erithacus rubecula) in response to simulated intrusions with or without experimental noise. First, we predicted that urban birds, living in noisier habitats, would be generally more aggressive than rural birds. We also predicted that during simulated intrusions with experimental noise, robins would increase their physical aggression and show a multi-modal shift, i.e., respond with more visual threat displays and sing fewer songs. Finally, we expected the multi-modal shift in response to noise to be stronger in urban birds compared to rural birds. The results showed that urban birds were more aggressive than rural robins, but an increase in aggression with experimental noise was seen only in the rural birds. Urban but not rural birds decreased their song rate in response to noise. Contrary to the multi-modal shift hypothesis, however, there was no evidence of a concurrent increase in visual signals. These results point to a complex role of immediate plasticity and longer-term processes in affecting communication during aggressive interactions under anthropogenic noise. Significance StatementHuman activity has an enormous effect on wildlife, including on their social behavior. Animals living in urban areas often tend to be more aggressive than those living in rural areas, which may be due to urban acoustic noise making communication between individuals more difficult. In a study with a common songbird, the European robin, we investigated the role of urban acoustic noise in aggression and territorial communication. Urban robins were more aggressive than rural robins, and additional noise in the territory increased aggression in rural but not urban robins. While urban robins decreased their singing effort with additional noise, they did not increase visual signals concurrently. These results suggest that noise can indeed make animals behave more aggressively although the effect may depend on how noisy it is already. These results further our understanding of how human-made noise changes animal communication and social behavior.

animal behavior and cognition↗

bioRxiv2020

Song sparrows do not discriminate between their own song and stranger song

Bird song is socially learned. During song learning, the birds hearing its own vocalization is important for normal development of song. Whether birds own song is represented and recognized as a special category in adult birds, however, is unclear. If birds respond differently to their own songs when these are played back to them, this would be evidence for auditory self-recognition. To test this possibility, we presented song sparrow males (Melospiza melodia) playbacks of their own songs or stranger songs and measured aggressive responses as well as type matching. We find no evidence of behavioral discrimination of birds own song relative to the (non-matching) stranger song. These findings cast doubt on an earlier proposal that song sparrows display auditory self-recognition and support the common assumption in playback experiments that birds own song is perceived as stranger song.

animal behavior and cognition↗

bioRxiv2019

Song overlapping, ambient noise and territorial aggression in great tits

Animals often communicate with each other in noisy environments where interference from the ambient noise and other signallers may reduce the effectiveness of signals. Signalling behaviours may also evolve to interfere with signals of their opponents, e.g. by temporally overlapping them with their own, such as the song overlapping behaviour that is seen in some songbirds during aggressive interactions. Song overlapping has been proposed to be a signal of aggressive intent, but few studies directly examined the association between song overlapping and aggressive behaviours of the overlapping bird (the predictive criterion). In the present paper we examined the question of whether song overlapping is correlated with aggressive behaviours displayed during a simulated territorial intrusion in a population of great tits (Parus major) living in an urban-rural gradient. We also examined whether aggressive behaviours are correlated with the ambient noise levels. We found that overlapping was associated negatively with aggressive behaviours males displayed against a simulated intruder. These results fail to support the predictive criterion for song overlapping, raising the question whether overlapping is in fact a signal of aggressive intent. Ambient noise levels were associated positively with aggressive behaviours but did not correlate with song rate, song duration or song overlapping. Great tits in noisy urban habitats may display higher levels of aggressive behaviours due to either interference of noise in aggressive communication or another indirect effect of noise.

animal behavior and cognition↗

bioRxiv2019

Territory establishment, song learning strategies and survival in song sparrows

In most songbirds the processes of song learning and territory establishment overlap in the early life of young birds who usually winds up with songs matching those of their territorial neighbors in their first breeding season. In the present study, we examined the relationships among the timing of territory establishment, the pattern of song learning and territorial success in a sedentary population of song sparrows (Melospiza melodia). Males in this population show high song sharing within neighborhoods derving from their learning most of their songs from neighboring males. These shared songs are preferentially used in interactions with neighbors. Males also show significant variation in the timing of territory establishment, ranging from their first summer until the next spring. Using a three-year dataset, we found that the timing of territory establishment did not systematically affect the composition of the song repertoire of the tutee: early establishers and late establishers learned equally as much from their primary tutors, and had a similar number of tutors and repertoire size. Timing of territory establishment also did not have an effect on subsequent survival on territory. Therefore, the song learning program of song sparrows seems versatile enough to lead to high song sharing even for birds that establish territories relatively late.

animal behavior and cognition↗

bioRxiv2019

Bird Song Learning is Mutually Beneficial for Tutee and Tutor

Song learning is generally assumed to be beneficial for a young songbird, but merely incidental, without costs or benefits, for the older song tutors. In the present study we contrast two mutually exclusive hypotheses about the tutor/tutee relationship: (1) that it is cooperative, or at least mutually tolerant, with tutor and tutee mutually benefiting from their relationship, vs. (2) that it is competitive, with tutor and tutee competing over territory, so that one or the other suffers negative fitness consequences of their relationship. In a field study of three consecutive cohorts of song sparrows (Melospiza melodia) we determined the older bird (primary tutor) from whom the young bird (tutee) learned most of his songs, and how long tutee and primary tutor survived subsequently. We found that the more songs a tutee learns from his primary tutor, the longer their mutual survival on their respective territories. This study provides the first evidence of a mutual benefit of bird song learning and teaching in nature.

animal behavior and cognition↗

bioRxiv2019

Male song sparrows modulate their aggressive signaling in response to plumage signals: experiments with 3-D printed models

Competitive interactions among conspecifics are often resolved by assessing signals that honestly indicate individual fighting ability or dominance. In territorial species, signals of competitive ability are thought to function primarily during the early stages of territory establishment, but recent evidence suggests that these signals continue to influence interactions with floaters and neighbors well after territory establishment. Here, we examine the influence of the extent of chest spotting displayed by an intruding male on the response of territorial male song sparrows. We exposed males to 3-D printed models with large or small spotting area coupled with conspecific playback and recorded their behavior. We also assessed the response of a subset of males to both the 3-D printed models and a traditional, taxidermic mount to ensure the 3-D models were a realistic stimulus. We found no differences in the number of attacks or proximity to the model due to spotting area. However, territorial males produced more soft songs and tended to sing fewer loud songs, both of which predict attack in our population, in response to the model with less chest spotting. One possibility is that males with less chest spotting elicit a stronger response because they are seen as a greater threat. Based on our previous findings in this system, we think it is more likely that models with less chest spotting are perceived as subordinate and therefore easier to defeat, leading to a stronger response by territory holders. We found males were equally likely to attack 3-D printed models and a taxidermic mount but signaled more aggressively during trials with the taxidermic mount than the 3-D printed models. This suggests that birds recognized the 3-D models as meaningful stimuli but that the use of 3-D printed models should be validated through comparison to a traditional taxidermic mount when possible.

animal behavior and cognition↗

bioRxiv2019

Multi-modal communication: Song sparrows increase signal redundancy in noise

Although the effects of anthropogenic noise on animal communication have been studied widely, most research on the effect of noise in communication has been on communication in a single modality. Consequently, how multimodal communication is affected by anthropogenic noise is relatively poorly understood. Here we ask whether song sparrows (Melospiza melodia) show evidence of plasticity in response to noise in two aggressive signals in acoustic and visual modalities. We test two hypotheses: (1) that song sparrows will shift signaling effort to the visual modality (the multi-modal shift hypothesis), and (2) that they will increase redundancy of their multi-modal signaling (the back-up hypothesis). We presented male song sparrows with song playback and a taxidermic mount with or without a low-frequency acoustic noise from a nearby speaker. We found that males did not switch their signaling effort to visual modality (i.e., wing waves) in response to the noise. However, the correlation between warbled soft songs and wing waves increased in the noise treatment, i.e. signals became more redundant. These results suggest that when faced with anthropogenic noise, song sparrows can increase redundancy of their multi-modal signals, which may aid in robustness of the communication system.

animal behavior and cognition↗

bioRxiv2018

Are signals of aggressive intent less reliable in urban habitats?

The effect of urban noise on animal communication systems is one of the best examples of how anthropogenic change affects animal social behaviour. Urban noise often drives shifts in acoustic properties of signals but the consequences of noise for the honesty of signals - that is, how well they predict signaler behaviour, is unclear. Here we examine whether honesty of aggressive signaling changes in urban living song sparrows (Melospiza melodia). Aggressive signaling in song sparrows consists of close-range signals in two modalities that predict a subsequent attack: the low amplitude soft songs (an acoustic signal) and wing waves (a visual signal). Male song sparrows living in urban habitats display more territorial aggression than males living in rural habitats, but whether the honesty of close-range signals is affected by urbanization has not been examined. If soft songs are less effective in urban noise, we predict that they would be less reliably associated with attack in these habitats compared to rural habitats. We found that while acoustic noise was higher in urban habitats, the urban birds still sang more soft songs than rural birds during a simulated territorial intrusion. Furthermore, high rates of soft songs and low rates of loud songs predicted attacks in both habitats. Finally, we found evidence for a potential multimodal shift: urban birds tended to give proportionally more wing waves than soft songs than rural birds. These results indicate that urbanization might have a limited effect on the overall honesty of aggressive signals in song sparrows.

animal behavior and cognition↗

bioRxiv2017

Male parental investment reflects the level of partner contributions and brood value in tree swallows

Biparental care presents an interesting case of cooperation and conflict between unrelated individuals. Several models have been proposed to explain how parents should respond to changes in each others parental care to maximize their own fitness, predicting no change, partial compensation, or matching effort as a response. Here, we present an experiment in tree swallows (Tachycineta bicolor) in which we increased the parental care of females by presenting them, but not their mates, with additional nestling begging calls using automated playbacks. We performed this experiment in two populations differing in future breeding opportunities and thus the intensity of conflict over current parental care. We found that in response to a temporary increase in female parental effort, males in the northern population with lower sexual conflict matched the increased effort, whereas males in the southern population did not. We also found that increases in parental care during playbacks were driven by the females (i.e., females initiated the increased effort and their mates followed them) in the northern population but not the southern population. These results support the idea that with incomplete information about the brood value and need, cues or signals from the partner might become important in coordinating parental care.

animal behavior and cognition↗

bioRxiv2017

Good tutors are not Dear Enemies in Song Sparrows

Bird song is the most widely studied example of vocal learning outside human language and shares important parallels with it, including the importance of social factors during development. Our understanding of how social factors affect song learning however remains surprisingly incomplete. Here we examine the possible role of aggressive interactions in determining song \"tutor\" choice in song sparrows (Melospiza melodia), a songbird in which individuals display song learning strategies ranging from learning primarily from one tutor, to learning a few songs each from a number of tutors. We test two hypotheses: The Competition hypothesis suggests that young birds learn more from tutors with whom they compete especially intensely and predicts that tutees will respond with high aggression to tutor songs. In contrast the Cooperation hypothesis suggests that song learning reflects a cooperative relationship between the tutor and the tutee and predicts that tutees will respond with low aggression to tutor songs. In a playback experiment we found that birds respond more aggressively to songs of their tutors than they do to songs of strangers and that the strength of aggressive response correlated positively with how much they had learned from that tutor. These results provide the first field evidence for the hypothesis that young males preferentially learn their songs from adult males with whom they compete most intensely during the song-learning phase, and perhaps afterwards.

animal behavior and cognition↗