02093nas a2200157   4500008004100000245013800041210006900179520149100248653002601739653001301765653003201778653001301810653001001823100003101833856007101864       2021                        eng d00aUse of simple graded signals in the long-distance vocal communication of a forest thrush ( <i>Catharus fuscescens</i>               )0 aUse of simple graded signals in the longdistance vocal communica3 a<p>I investigated the use of simple graded structures (i.e. &lsquo;calls&rsquo;) in long-distance vocal communication among territorial forest-dwelling Catharus fuscescens &ndash; 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 &ndash; either precisely or imprecisely &ndash; 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&rsquo;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.</p>
10aAssessment/Management10aCatharus10amotivation-structural rules10aSongbird10aVeery1 aHeckscher, Christopher, M.  uhttps://www.tandfonline.com/doi/full/10.1080/09524622.2021.1888316