@article {58415, title = {Use of simple graded signals in the long-distance vocal communication of a forest thrush ( Catharus fuscescens )}, year = {2021}, abstract = {

I investigated the use of simple graded structures (i.e. \‘calls\’) in long-distance vocal communication among territorial forest-dwelling Catharus fuscescens \– an oscine passerine that also possesses a complex song. Two experiments were conducted: (1) Nests were threatened in three different contexts to test the effect of increasing motivation on three response variables (call form, rate, amplitude), and (2) a playback study was undertaken to quantify the accomplishments of graded call structures on territory-holders. Results from the two experiments showed that long-distance communication in the focal species is dependent on two concurrent aspects of communication: (1) Acoustic cues to signaller motivation via call rate, (2) spectral cues that reveal directivity \– either precisely or imprecisely \– that complement the perception of signaller location via distance assessment (ranging). Simultaneously, amplitude and bandwidth are adjusted to beam signals across various distance intervals. Therefore, to affect conspecific behaviour, a signaller can alter vocal cues to manipulate an assessor\’s perception of signaller location while revealing motivation. This study reveals the foundational components of short and long-distance communication with the use of simple graded calls by a forest-dwelling oscine passerine. It is similar to long-distance communication networks documented in some parrots, marine mammals, and primates.

}, keywords = {Assessment/Management, Catharus, motivation-structural rules, Songbird, Veery}, doi = {10.1080/09524622.2021.1888316}, url = {https://www.tandfonline.com/doi/full/10.1080/09524622.2021.1888316}, author = {Heckscher, Christopher M.} } @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.} } @article {57582, title = {Habitat-related differences in song structure and complexity in a songbird with a large repertoire}, journal = {BMC Ecology}, volume = {19}, year = {2019}, month = {Jan-12-2019}, abstract = {

Background

Urbanisation has been shown to influence many aspects of animal vocal communication. Much attention has been paid to anthropogenic noise, which is often described as one of the most challenging disturbances for urban dwellers. While a large body of literature describes associations between vocal behavior of avian populations and background noise level, most of these studies were conducted on species with relatively simple songs and small repertoire sizes. This study focuses on the song thrush, Turdus philomelos, a common Eurasian songbird with a complex singing style and large syllable repertoire. Our objective was to determine whether frequency, repertoire and temporal organisation of song parameters vary between birds inhabiting urban and adjacent forest habitats in which ambient noise levels differ.

Results

Songs of urban males were found to be more complex than in conspecifics from natural forest populations. Urban dwellers possessed greater syllable repertoires and repeated syllable sequences more often. In addition, they used a smaller proportion of whistles and a higher proportion of twitter syllables when singing compared to the nonurban males. Moreover, we found significant differences in the minimum and peak frequency of the whistle syllable between studied populations.

Conclusions

These findings may be an example of adaptation of acoustic communication in noisy urban environments, but we also discuss other possible explanations. We emphasize the need for further investigation into the relationships between birdsong and habitat characteristics, male quality, population density and ambient noise level in populations occupying urban and nonurban habitats.

}, keywords = {animal communication, anthropogenic noise, birdsong, songbirds, Turdus philomelos, Urban ecology, urbanisation}, doi = {10.1186/s12898-019-0255-7}, url = {https://bmcecol.biomedcentral.com/articles/10.1186/s12898-019-0255-7}, author = {Deoniziak, Krzysztof and Osiejuk, Tomasz S.} } @article {53373, title = {A new statistical method to test equivalence: an application in male and female eastern bluebird song}, journal = {Animal Behaviour}, volume = {145}, year = {2018}, month = {Jan-11-2018}, pages = {77 - 85}, keywords = {eastern bluebird, equivalence testing, female song, hypothesis testing, publication bias}, issn = {00033472}, doi = {10.1016/j.anbehav.2018.09.004}, url = {https://linkinghub.elsevier.com/retrieve/pii/S0003347218302744https://api.elsevier.com/content/article/PII:S0003347218302744?httpAccept=text/xmlhttps://api.elsevier.com/content/article/PII:S0003347218302744?httpAccept=text/plain}, author = {Rose, Evangeline M. and Mathew, Thomas and Coss, Derek A. and Lohr, Bernard and Omland, Kevin 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 {52563, title = {Do birds differentiate between white noise and deterministic chaos?}, journal = {Ethology}, volume = {123}, year = {2017}, month = {Jan-12-2017}, pages = {966 - 973}, abstract = {

Noisy, unpredictable sounds are often present in the vocalizations of fearful and stressed animals across many taxa. A variety of structural characteristics, called nonlinear acoustic phenomena, that include subharmonics, rapid frequency modulations, and deterministic chaos are responsible for the harsh sound quality of these vocalizations. Exposure to nonlinear sound can elicit increased arousal in birds and mammals. Past experiments have used white noise to test for effects of deterministic chaos on perceivers. However, deterministic chaos differs structurally from white noise (i.e., random signal with equal energy at all frequencies), and unlike white noise, may differ dramatically depending on how it is produced. In addition, the subtle structural variation of chaos may not be distinguishable in the environment due to the attenuation and degradation of sound over distance and different habitat types. We designed two experiments to clarify whether American robins (Turdus migratorius) and warbling vireos (Vireo gilvus) discriminate between white noise and deterministic chaos. We broadcast and re-recorded white noise and two exemplars of deterministic chaos\—one generated with a Chua oscillator and the other generated using a logistic equation\—at 1, 10, 20, 30, 40, and 80 m across open and forested habitat and used spectrogram correlations to compare stimuli along this degradational gradient. We found that sounds degraded similarly in both habitats when compared to a reference distance of 1 m. Comparing pairs of stimuli across distances suggested that Chua chaos was more easily distinguishable from noise and logistic chaos. In addition, all stimuli became more distinctive over increased distance. The second experiment tested behavioral responses of robins and warbling vireos to control sounds of tropical kingbird (Quiscalus mexicanus), white noise, and two exemplars of deterministic chaos (Chua and logistic). Neither American robins nor warbling vireos responded differently to at least two types of deterministic chaos and white noise, validating previous playback studies that used white noise as a surrogate for deterministic chaos. Uniform responses to a variety of nonlinear features in these birds possibly reflect error management in alarm signal detection.

}, doi = {10.1111/eth.2017.123.issue-1210.1111/eth.12702}, url = {http://doi.wiley.com/10.1111/eth.2017.123.issue-12}, author = {Blumstein, Daniel T. and Whitaker, Jessica and Kennen, Judith and Bryant, Gregory A.}, editor = {Koenig, W.} } @article {52528, title = {Eavesdropping avoidance and sound propagation: the acoustic structure of soft song}, journal = {Animal Behaviour}, volume = {134}, year = {2017}, month = {Jan-12-2017}, pages = {113 - 121}, abstract = {Many species use low-amplitude (soft) song during close range interactions with conspecifics, such as in aggressive encounters or courtship displays. It has been suggested that soft song is adapted to limit eavesdropping by conspecifics or predators through reduced signal transmission range. If so, other structural features of soft song, besides amplitude, should be adapted to reduce transmission. The soft songs of white-throated thrushes, Turdus assimilis, have properties expected to lower transmission, such as higher frequency and broader bandwidth relative to broadcast songs. We compared the transmission properties of broadcast and soft syllables using a sound propagation field experiment. When played at the same amplitude as broadcast song, soft song showed greater excess attenuation and blur ratios and lower signal-to-noise ratios. Lowering the frequency of soft syllables recovered similar transmission properties as those of broadcast syllables. Further analysis of spectral traits showed that excess attenuation values were mainly affected by minimum frequency and peak frequency, while blur ratio variation was predominantly affected by bandwidth, and signal-to-noise ratios were predicted by bandwidth and peak frequency. Additionally, soft song had more frequency overlap with background noise than broadcast song. These results support the eavesdropping hypothesis: aspects of the acoustic structure of soft signals in addition to low amplitude seem to have been shaped by selection to reduce transmission and avoid eavesdroppers.}, keywords = {communication range, signal design, song mode, sound degradation, sound transmission, Turdus, whispered communication}, issn = {00033472}, doi = {10.1016/j.anbehav.2017.10.008}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0003347217303329}, author = {Vargas-Castro, Luis E. and Sandoval, Luis and Searcy, William A.} }