Response to Kroodsma's critique of banded wren song performance research

of Vehrencamp et al. (2013) is totally unwarranted. We merely stated the general theoretical proposition being tested in our study, a standard protocol for scientific articles. The statement was fully justified given the large literature on performance constraints affecting sound production and the association of acoustic signal features with aspects of sender characteristics. Kroodsma does not appear to question the results, which showed that trill note consistency and frequency bandwidth increase with male age. We also discovered that trill note rate for a given song type increases during playback experiments in relation to the male's level of aggressive response, a result that has now been found in other species (Funghi, Cardoso, & Mota, 2015; Linhart, Jaska, Petruskova, Petrusek, & Fuchs, 2013). Thus this aspect of performance seems to provide cues to receivers about a rival's immediate aggressive motivation. We did not find any associations with male survival or our measure of body condition. Our results and interpretations were not biased by any desire to support or disprove the hypothesis, and in several instances we offered alternative hypotheses where appropriate. Commenting further on this paper, Kroodsma (2017, page e14) writes (his italics): ‘According to the scatterplot of trill rate and bandwidth for banded wrens (Fig. 11), relatively few songs are difficult to execute as defined in this performance context, because most songs fall far from the upper bound on the graph. Every male ‘willingly’ learnsmany ‘low-performance’, easy-to-execute songs in order to have particular song types in his repertoire, as if performance did not matter, as if there were no selection for difficult-toexecute songs as claimed in this paper’. Repertoire species such as the banded wren use contrasting song types to emphasize switching rates, short-term diversity and matching during territorial interactions (Molles, 2006; Vehrencamp et al., 2007, 2014). But Kroodsma has conveniently ignored another component of banded wren trills: their varied and complex note shapes as mentioned earlier. Trill note consistency is a third axis of performance in this species, and we showed in this paper (Vehrencamp et al., 2013, see supplementary online material) that consistency and vocal deviation trade off (are negatively correlated) within males and song types. Thus, song types far from the trill rate versus bandwidth upper limit are not necessarily easy to execute, as they may have a complex shape that is difficult to repeat consistently. Kroodsma concludes that we still await good answers to the question of what information listeners extract about singers from their songs beyond species identification. In fact, there is a growing body of data showing that aspects of vocal performance, including trill rate, vocal deviation, frequency excursion, trill note and song consistency and call rate/call duration trade-offs, do provide useful information to receivers in some species and are associated with reproductive benefits in many birds, mammals, anurans and crickets (e.g. Botero et al., 2009; Byers, Akresh,& King, 2015; Funghi et al., 2015; Linhart et al., 2013; Pasch, George, Campbell, & Phelps, 2011; Petruskova et al., 2014; Podos et al., 2016; Reichert & Gerhardt, 2012; Sprau, Roth, Amrhein, & Naguib, 2013; Wagner, Beckers, Tolle, & Basolo, 2012; Welch, Smith, & Gerhardt, 2014). Our studies have contributed to this body of knowledge, specifically by demonstrating the existence of cues to age and aggressive motivation, alongwith the strategic use of song type use patterns to indicate approach and retreat during territorial negotiations.