RESEARCH PAPER A Tradeoff Between Performance and Accuracy in Bird Song Learning David C. Lahti* , Dana L. Moseley* & Jeffrey Podos* * Department of Biology, University of Massachusetts, Amherst, MA, USA  Department of Biology, Queens College, City University of New York, Flushing, NY, USA Introduction Imitative learning is a widespread means of acquir- ing patterns of behavior (Whiten 1992; Zentall 2006). When imitation is precise and rooted in an ecological function, the behavioral pattern tends to remain stable over time (Henrich & Boyd 1998; Claidie ` re & Sperber 2010; Lindeyer & Reader 2010). This stability can preserve or even be vital to the effectiveness of a behavior, as in communication where signals are shared among individuals (Nowicki & Searcy 2005). Decades of research in the model systems of human speech and bird song, for exam- ple, have shown that juveniles memorize and accu- rately reproduce sounds produced by their elders (Slater 1989; Kuhl & Meltzoff 1996; Brainard & Doupe 2002; Pagel 2009). Such accuracy is made possible not only by an advanced ability to imitate sounds, but also by an unlearned bias toward learn- ing sounds of one’s own species or genetic lineage (Marler & Peters 1977; Soha & Marler 2000; Dediu & Ladd 2007). Accurate and species-specific imitation cannot explain the origins of behavioral novelty, about which less is known. In general, new variations in behavioral patterns can arise through creative depar- tures from imitation. Some novelties might arise through random copy errors (Slater 1989). Another Correspondence David C. Lahti, Department of Biology, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 10541, USA. E-mail: david.lahti@qc.cuny.edu Received: March 2, 2011 Initial acceptance: April 14, 2011 Final acceptance: June 13, 2011 (L. Ebensperger) doi: 10.1111/j.1439-0310.2011.01930.x Abstract Some of nature’s most complex behaviors, such as human speech and oscine bird song, are acquired through imitative learning. Accurate imi- tative learning tends to preserve patterns of behavior across generations, thus limiting the scope of cultural evolution. Less well studied are the routes by which cultural novelties arise during development, beyond simple copy error. In this study we assess, in a species of songbird, the relationship in song learning between two potentially conflicting learn- ing goals: accuracy in copying and maximization of vocal performance. In our study species, the swamp sparrow (Melospiza georgiana), vocal per- formance can be defined for a given song type and frequency range by the rate of note repetition (‘trill rate’), with faster trills being more diffi- cult to sing. We trained young swamp sparrows with song models with experimentally modified trill rates and characterized both the accuracy and performance levels of copies. Our main finding is that birds elevated the trill rates of low-performance models, but at the expense of imitative accuracy. By contrast, birds reproduced normal and high-performance models with typically high accuracy in structure and timing. Develop- mental mechanisms that enable songbirds to balance imitative accuracy and vocal performance are likely favored by sexual selection and may help explain some current patterns of variation in birdsong. Such mech- anisms may also explain how behaviors that are learned by imitation can nevertheless respond to selection for high-performance levels in their expression. Ethology Ethology 117 (2011) 1–10 ª 2011 Blackwell Verlag GmbH 1