@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 {58248, title = {An experimental investigation of the bioacoustics of cowbird song}, year = {1981}, abstract = {

Female cowbirds (Molothrus ater ater), maintained in isolation from males during the breeding season, respond to the playback of male song with copulatory postures. They respond to some songs more than to others. Cowbird song potency can thus be operationally defined by the proportion of copulatory postures a song elicits across multiple playbacks. The purpose of the present study was to explore whether song potency changes with distance in the field. No field recordings elicited high levels of responding by the females. When songs of known high potency are systematically degraded, the results indicate that female cowbirds are sensitive to small changes in signal to noise ratio and to atmospheric attenuation. The data suggest that cowbird song potency degrades very rapidly with transmission distance in the field.

}, doi = {10.1007/BF00302940}, url = {http://link.springer.com/10.1007/BF00302940}, author = {King, Andrew P. and West, Meredith J. and Eastzer, David H. and Staddon, J. E. R.} } @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 {17198, title = {Why do caterpillars whistle at birds? Insect defence sounds startle avian predators}, journal = {Behavioural Processes}, year = {2017}, month = {Jan-02-2017}, issn = {03766357}, doi = {10.1016/j.beproc.2017.02.002}, url = {http://linkinghub.elsevier.com/retrieve/pii/S0376635716303655}, author = {Dookie, Amanda L. and Young, Courtney A. and Lamothe, Gilles and Schoenle, Laura A. and Yack, Jayne E.} }