@article {58311, title = {Does the presence of an observer affect a bird{\textquoteright}s occurrence rate or singing rate during a point count?}, year = {2020}, abstract = {

The approach or presence of an observer may affect the behavior of nearby birds, rendering them either more or less detectable than when no observer is present due to a change in singing rates. To test whether there are systematic detection biases associated with the presence of an observer during point count bird surveys, we compared the occurrence and singing rates of birds during a 10-min period immediately preceding the time when an observer arrived to conduct a count and during the formal count itself by extracting song information from autonomous sound recorders. We obtained recordings of 36 species of birds detected at \≥5 locations in one of three vegetation types, including burned conifer forest, green conifer/riparian streamside forest, and riparian bottomland/marshland. We found that species richness and both the probability of occurrence and singing rate for any of the species recorded were unaffected by the presence of an observer. In addition, the probability of occurrence did not differ significantly among four 2.5-min recording sessions during 10-min counts when an observer was present. Thus, the presence of an observer did not appear to introduce any detectable systematic bias that would make bird lists or unadjusted occurrence rates inaccurate on that basis alone. In addition, rates of bird occurrence across 2.5-min temporal subsets of a 10-min count did not vary in a systematic way that would violate the assumption of equal occupancy across adjacent time periods as sometimes used to build detection histories in occupancy modeling.

}, keywords = {bird survey, detectability, observer effect, occupancy, passive acousticsampling, point count, singing rate, utonomous recording unit}, doi = {10.1111/jofo.12329}, url = {http://doi.wiley.com/10.1111/jofo.12329}, author = {Hutto, Richard L. and Hutto, Russell R.} } @mastersthesis {58198, title = {Divergent selection and reproductive isolation: an empirical study on reed buntings}, year = {2020}, abstract = {

Divergent selection and local adaptation are responsible for many phenotypic differences between populations, potentially leading to speciation through the evolution of reproductive barriers. Acoustic divergence, in particular, is often the basis of assortative mating and behavioral isolation in birds. However, some species have different singing styles used in distinct social contexts, and songs of each style may change at different rates over time and space. Mate recognition largely depends on learning, generally resulting in discrimination against nonlocal stimuli. Nevertheless, there may also be geographical variation in discrimination, allowing inference on the mechanisms behind recognition. Morphologic divergence can cause reproductive isolation too, and a strong association between bill traits and foraging niche, at a given place and time, may indicate ecological speciation is at play and how.
This thesis focused on reed buntings (Emberiza schoeniclus), a small passerine that breeds in marshlands throughout the Palearctic. Populations of three subspecies were studied: migratory E. s. schoeniclus, breeding in northern and central Europe; and the residents E. s. lusitanica from northwest Iberia and E. s. witherbyi from southeast Iberia and southern France (hereafter schoeniclus, lusitanica and witherbyi, respectively).
Four main objectives were addressed using different approaches: (1) phenotypic divergence was evaluated to determine the extent of local adaptation to migration and diet, using linear measurements and geometric morphometrics; (2) song divergence between subspecies and between the three singing styles of each subspecies were tested searching for effects of sexual selection, using spectral traits and derived synthetic variables; (3) song discrimination level was determined to infer premating reproductive isolation, using playback of fast song to test territorial males; (4) association between bill morphology and foraging niche was evaluated searching for evidence of natural selection, by sampling blood in southwest Europe during the winter (when target subspecies co-occur) and performing stable isotope analyses (carbon and nitrogen).
As predicted, migratory subspecies were smaller and had longer and more pointed wings. Unexpectedly, their tail was longer, probably due to correlation with wing length. witherbyi, which feed on insects hiding inside reed stems during the winter, had a very thick bill; whereas schoeniclus, which feed on seeds, had thinner bills. Although smaller, lusitanica had thicker and longer bill than schoeniclus. Geometric morphometrics revealed that southern subspecies have a more convex culmen than schoeniclus, and that lusitanica and schoeniclus bills differ more in shape than in linear measurements. The two singing styles under sexual selection (dawn and fast songs, related to obtaining extrapair and social mates, respectively) diverged more than the slow songs (an all-clear signal to nest attending females). Multiple song traits differed between subspecies in all styles, with intermediate values for lusitanica. Cluster analyses of populations indicate that sexually selected styles better discriminate subspecies, describing a major split in song features between schoeniclus and the resident subspecies. It was found that witherbyi, and to some extent lusitanica, males largely ignored schoeniclus songs. However, witherbyi reacted less strongly to lusitanica than the converse. In contrast, schoeniclus males reacted equally strongly to all subspecies. schoeniclus showed a broader isotopic niche than southern subspecies, which seemed similar despite witherbyi more divergent bill. Stable isotope ratios were consistent with resident subspecies feeding on C3-plant-feeding insects, whereas schoeniclus diet also included C4 plant material.

Subspecies differing in several traits as theoretically predicted indicate local adaptation through natural selection. Greater song divergence in fast and dawn styles implies that sexual selection is important in this evolutionary process. Differential territorial defense provides evidence of premating reproductive isolation, and discrimination by southern subspecies seems associated with local adaptation. Recognition pattern agrees with ecological rather than neutral divergence, as predicted in ecological speciation processes. Isotopic niche divergence between northern and southern subspecies suggests that bill differentiated by natural selection through competition during winter.

}, keywords = {acoustic divergence, asymmetric recognition, bill, birdsong, Emberiza schoeniclus, geometric morphometrics, isotopic niche, local adaptation, morphologic divergence, playback, singing style, song discrimination, speciation, subspecies}, author = {Lu{\'\i}s de Oliveira Rijo Gordinho} } @article {57599, title = {Extraordinary variation in a simple song: No geographical patterns in initial phrase variation of the Yellowhammer, a passerine with pronounced dialectsAbstract}, year = {2019}, abstract = {

Geographical variation of birdsong is used to study various topics from cultural evolution to mechanisms responsible for reproductive barriers or song acquisition. In species with pronounced dialects, however, patterns of variation in non-dialect parts of the song are usually overlooked. We focused on the individually variable initial phrase of the song of the Yellowhammer (Emberiza citrinella), a common Palearctic passerine which became a model species for dialect research. We used a quantitative method to compare the similarity of initial phrases from the repertoires of 237 males recorded at different spatial scales in a central European country covering all main dialect types. We hypothesized that patterns of initial phrase sharing and/or phrase similarity are affected by dialect boundaries and geographical proximity (i.e. that birds from the same dialect regions use more similar phrases or share them more often). Contrary to our expectations, initial phrase variation seems unrelated to dialects, as we did not find higher similarity either among recordings from the same dialect areas or among those from the same locality. Interestingly, despite the immense variability of phrase types detected (only 16\% of 368 detected initial phrase types were shared between at least 2 males), a relatively high proportion of males (45\%) was involved in sharing, and males using the same initial phrase were located anywhere from tens of meters to hundreds of kilometers apart. The patterns of variation suggest that precise copying during song learning as well as improvisation play important roles in forming individual repertoires in the Yellowhammer. Our data also confirm previous indications that the repertoires of Yellowhammer males (i.e. the composition of initial phrases) are individually unique and temporally stable. This makes the species a good candidate for individual acoustic monitoring, useful for detailed population or behavioral studies without the need for physical capture and marking of males.

}, doi = {10.1093/auk/ukz055}, url = {https://academic.oup.com/auk/article/doi/10.1093/auk/ukz055/5601449}, author = {van Boheemen, Sharina J and Dibl{\'\i}kov{\'a}, Lucie and B{\'\i}lkov{\'a}, Jana and Petrusek, Adam and Petruskov{\'a}, Tereza} } @article {57346, title = {Evidence for differing trajectories of songs in urban and rural populations}, journal = {Behavioral Ecology}, year = {2019}, month = {Jul-08-2020}, abstract = {

Learned traits, such as foraging strategies and communication signals, can change over time via cultural evolution. Using historical recordings, we investigate the cultural evolution of birdsong over nearly a 50-year period. Specifically, we examine the parts of white-crowned sparrow (Zonotrichia leucophrys nuttalli) songs used for mate attraction and territorial defense. We compared historical (early 1970s) recordings with contemporary (mid-2010s) recordings from populations within and near San Francisco, CA and assessed the vocal performance of these songs. Because birds exposed to anthropogenic noise tend to sing at higher minimum frequencies with narrower frequency bandwidths, potentially reducing one measure of song performance, we hypothesized that other song features, such as syllable complexity, might be exaggerated, as an alternative means to display performance capabilities. We found that vocal performance increased between historical and contemporary songs, with a larger effect size for urban songs, and that syllable complexity, measured as the number of frequency modulations per syllable, was historically low for urban males but increased significantly in urban songs. We interpret these results as evidence for males increasing song complexity and trilled performance over time in urban habitats, despite performance constraints from urban noise, and suggest a new line of inquiry into how environments alter vocal performance over time.

}, keywords = {anthropogenic noise, birdsong, Cultural evolution, sexual selection, Urbanization, vocal performance}, issn = {1045-2249}, doi = {10.1093/beheco/arz142}, url = {https://academic.oup.com/beheco/advance-article/doi/10.1093/beheco/arz142/5551107}, author = {Moseley, Dana L and Jennifer N. Phillips and Derryberry, Elizabeth P and David A. Luther}, editor = {Candolin, Ulrika} } @article {53582, title = {Noise-induced vocal plasticity in urban white-crowned sparrows does not involve adjustment of trill performance components}, journal = {Scientific Reports}, volume = {9}, year = {2019}, month = {Jan-12-2019}, abstract = {

Background noise can interfere with acoustic communication and subsequently influence signaling behavior. Immediate signaling flexibility (ISF) is a context-dependent form of behavioral plasticity that allows animals to temporarily change their acoustic behavior in response to noise fluctuations and potentially improve the chances of successful communication in noisy environments. The adaptive value of ISF is ultimately contingent on the response of the intended receiver, and there are differential effects on receiver response depending on which signal component is modified. However, there is scant research on whether ISF involves modification of a signal component specifically linked to mate attraction or territory defense. Our study addresses this knowledge gap and provides important insight into whether males employ short-term signal modification in a manner that could affect mate pairing success in birds. Specifically, we explore the maladaptive potential of ISF in the San Francisco, California population of Zonotrichia leucophrys nuttalli by testing for changes in trill bandwidth and rate\—the specific trill structure components known to influence the receiver\’s perception of vocal performance in this species\—before and during noise broadcast experiments. Although Zonotrichia leucophrys nuttalli are capable of ISF, we found no evidence that noise induces temporary adjustment of the trill structure traits used by receivers to assess vocal performance.

}, doi = {10.1038/s41598-018-36276-5}, url = {http://www.nature.com/articles/s41598-018-36276-5}, author = {Gentry, Katherine E.} } @article {53369, title = {Soft songs in male ortolan buntings are used in an aggressive context but are not an aggressive signal}, journal = {Ethology}, volume = {124}, year = {2018}, month = {Jan-08-2018}, pages = {549 - 558}, abstract = {

Many bird species produce low-amplitude acoustic signals that have been poorly studied in comparison with loud, broadcast songs used for mate attraction and repelling rivals. In some birds, these soft signals were found to be emitted in an antagonistic context and were the most reliable predictor of a subsequent physical attack. The function of this signal is poorly understood, and several hypotheses have been proposed to explain the mechanisms and possible functions of such low-amplitude signals. The subject of this study is the ortolan bunting, a small passerine species that produces soft songs during territorial defence. In this study, we aim to study whether the soft songs of the ortolan bunting are a signal of increased aggressiveness by testing if they meet the context, prediction and response criteria of aggressive signals. We simulated stranger male intrusion into a focal male territory with three different playback experiments. We found no significant differences in the male responses to the taxidermic model regardless of whether they were or were not producing soft songs in response. The males responded more strongly to loud songs than to soft songs during the simulated intrusions, and the males did not treat soft songs as a predictor of conflict escalation. Although soft songs clearly appeared during territorial encounters and were not present during spontaneous singing before the intrusions, our results did not support the hypothesis that soft songs indicate aggressive character. We suggest that soft songs in the ortolan bunting are intentionally used by birds to modify their intentions or target-specific individuals within a close range.

}, keywords = {Aggressive signals, ortolan bunting, soft song, territorial defence}, doi = {10.1111/eth.2018.124.issue-810.1111/eth.12758}, url = {http://doi.wiley.com/10.1111/eth.2018.124.issue-8}, author = {Jakubowska, Aleksandra and Osiejuk, Tomasz S.}, editor = {Fusani, L.} } @article {53261, title = {Sing softly to evoke a response only from a recent intruder}, journal = {Behavioural Processes}, volume = {157}, year = {2018}, month = {Jan-12-2018}, pages = {244 - 249}, abstract = {

Low-amplitude soft songs have been described in many birds, but in most species, research has addressed only broadcast songs. Soft songs may have a similar or distinctive structure in comparison to broadcast songs produced in order to defend a territory and attract females. In some species, such soft songs were found to be produced in an aggressive context and were the best predictors of conflict escalation and later physical attack. However, such observations are not consistent across all species studied. Several hypotheses have been put forward to explain the function(s) of soft songs and why they are so quiet. Studies on the ortolan bunting (Emberiza hortulana) show that males produce soft songs similar in structure to broadcast songs during close interactions with conspecific intruders. However, experiments with the playback of loud and soft songs as well as taxidermic mount presentation revealed that soft song in this species does not fulfil aggressive signal criteria. Here we performed an experiment with two loudspeakers simulating movements of the intruder in order to test whether the soft songs are used to evoking a response from a nearby but not localised rival. We found that males responded with similar strength to songs played back from single and double speaker systems. Simultaneously, males produced more soft songs during and just after the phase of the experiment in which we simulated short flights of the intruder. Our results indicate that soft songs might be used during close interactions with rivals without being an aggressive signal and are used as short-range signals to check if the rival is still around. Our results also provide an alternative explanation of soft song behaviour in comparison to the hypotheses of eavesdropping avoidance and readiness to fight.

}, keywords = {Aggressive signals, Emberiza hortulana, playback experiment, Territory defence}, issn = {03766357}, doi = {10.1016/j.beproc.2018.10.012}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0376635718301335https://api.elsevier.com/content/article/PII:S0376635718301335?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0376635718301335?httpAccept=text/plain}, author = {Jakubowska, Aleksandra and Osiejuk, Tomasz S.} } @article {52600, title = {Spatiotemporal patterns of avian vocal activity in relation to urban and rural background noise}, journal = {Journal of Ecoacoustics}, volume = {1}, year = {2017}, month = {Apr-26-20172062}, pages = {Z9TQHU}, abstract = {

Background noise can interfere with and influence acoustic communication behavior. Signal interference is dependent on the amplitude and spectral characteristic of background noise, which varies over space and time. The likelihood of signal interference is greater when background noise is concentrated within the same frequency bands of an animal\’s vocalization, but even a partial masking effect can elicit signaling behavior modification. Relative to a rural landscape, background noise in an urban landscape is disproportionately comprised by anthropogenic sound, which fluctuates in amplitude throughout the day and occurs primarily in low frequencies (0\–2 kHz). In this study, we examined if urban-rural differences in vocal activity patterns exist in a species Zonotrichia leucophrys nuttalli that communicates above the frequency range of anthropogenic noise (2\–8 kHz). We tested whether vocal activity patterns changed in relation to sound in the high or low frequency bands within and between urban and rural locations. Automated acoustic recording devices (ARDs) continuously recorded throughout the morning song chorus, 0500 to 1,100 h, during the 2014 breeding season in San Francisco (urban) and Marin (rural) Counties, CA. Supervised learning cluster analysis was used to quantify vocal activity by totaling the number of songs. In general, vocal activity was greater in urban locations compared to rural locations. However, within rural and urban study sites, we found vocal activity decreased where low frequency noise levels were higher. There was not a relationship between vocal activity and high frequency, biotic sound. In both urban and rural locations, low frequency noise levels increased through the morning, while vocal activity remained relatively consistent. Our results demonstrate how patterns of vocal activity can change with low frequency, abiotic noise, even when there is no direct spectral overlap with the acoustic signal.

}, doi = {10.22261/JEA10.22261}, author = {Gentry, Katherine E.} } @article {52597, title = {Vocalizing during gaps in anthropogenic noise is an uncommon trait for enhancing communication in songbirds}, journal = {Journal of Ecoacoustics}, volume = {1}, year = {2017}, month = {Jul-06-20172238}, pages = {TLP16D}, abstract = {

Mounting evidence suggests that anthropogenic noise negatively impacts many wildlife species, including songbirds. One mechanism by which noise affects songbirds may be through acoustic obstruction to their systems of vocal communication. However, many species increase the amplitude or pitch of their vocalizations, which may partially mitigate the impact of high noise levels. When the amplitude of anthropogenic noise varies over time, such as near a moderate-use highway, short gaps between noise events may also provide an important opportunity for communication. But, whether songbirds adjust vocalization rates rapidly to avoid overlap with noise is unknown for most species. We used acoustic playback to expose songbirds to simulated road noise during the dawn chorus in otherwise quiet habitats. We measured vocalization rates under ambient conditions and during quiet gaps embedded within playback of road noise to assess whether a community of songbirds, and nineteen individual species, vocalize more regularly during noise gaps. There were no significant differences in community-wide acoustic output. Species-specific analysis revealed that only four species altered their vocal rates during quiet gaps in noise, but that the direction of the effect varied by species. Point count results revealed that birds generally remained on site for the duration of the experiment, suggesting that abandonment of noisy locations was unlikely to confound our results. In sum, increasing vocal output during short gaps in noise occurred in only a handful of species, perhaps contributing to the limited number of species that are found within noisy habitats.

}, doi = {10.22261/JEA10.22261/JEA.TLP16D}, author = {Proppe, Darren S. and Finch, Emily} } @article {52580, title = {Introductory whistle is sufficient for early song recognition by golden-crowned sparrow nestlings}, journal = {Animal Behaviour}, volume = {133}, year = {2017}, month = {Jan-11-2017}, pages = {83 - 88}, abstract = {

Many songbird species have a predisposition to learn conspecific songs, suggesting song learning may be guided by an innate auditory template. Evidence for such a template includes preferential response to conspecific song in early life, even before song learning begins. A prime example of an innate cue for selective song learning is the introductory whistle of white-crowned sparrows, Zonotrichia leucophrys. The songs of its sister species, the golden-crowned sparrow, Zonotrichia atricapilla, also contain an introductory whistle, which differs in structure from that of white-crowned sparrows. Here we tested the ability of nestling golden-crowned sparrows in a sympatric population to discriminate between conspecific and heterospecific songs based on introductory whistles alone, prior to the onset of song learning. Golden-crowned sparrow nestlings responded with more chirps to playbacks of conspecific whistles than to heterospecific (white-crowned sparrow) whistles, and they responded similarly to full conspecific songs and conspecific whistles alone. We suggest that the introductory whistle alone is sufficient for song recognition in the golden-crowned sparrow. We discuss similarities and differences in the role of the introductory whistle between these sister taxa, and how this divergent song phrase may share a role in species recognition in both sister species. Identifying the cues underlying song recognition prior to song learning could be key to understanding the evolution of behavioural isolation between closely related songbird species.

}, keywords = {acoustic template, song learning, species recognition, whistles, Zonotrichia}, issn = {00033472}, doi = {10.1016/j.anbehav.2017.09.018}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0003347217303056}, author = {Hudson, Emily J. and Shizuka, Daizaburo} } @article {50504, title = {Good tutors are not dear enemies in song sparrows}, journal = {Animal Behaviour}, volume = {129}, year = {2017}, month = {Jan-07-2017}, pages = {223 - 228}, abstract = {

Birdsong 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 responded more aggressively to songs of their tutors than they did 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.

}, keywords = {aggression, communication, cooperation, social learning, song learning}, issn = {00033472}, doi = {10.1016/j.anbehav.2017.05.026}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0003347217301719}, author = {Ak{\c c}ay, {\c C}a{\u g}lar and Campbell, S. Elizabeth and Beecher, Michael D.} }