![]() ![]() How evolution shapes the timing and selectivity of learning has received considerable theoretical attention ( Lachlan and Servedio, 2004 Olofsson et al., 2011 Verzijden et al., 2012) and, in a few cases, has been demonstrated empirically with adult mate choice ( Grant and Grant, 1996 Magurran and Ramnarine, 2005). The effects of early sensory experience have been studied in many taxa in the context of mate choice ( Hebets, 2003 Verzijden and ten Cate, 2007 Balakrishnan et al., 2009 Delaney and Hoekstra, 2018) as well as in non-mating contexts ( Colombelli-Négrel et al., 2012 König et al., 2015). Juvenile experience can set the stage for behavior later in life. This study provides the first evidence that song discrimination at the onset of song learning is robust to the presence of closely related heterospecifics in nature, which may be an important adaptation in sympatry between potentially interbreeding taxa. However, although many songbirds hear and respond to acoustic signals before fledging, golden-crowned sparrow nestlings that heard different amounts of heterospecific song did not behave differently in response to heterospecific playbacks. ![]() We characterized the amount of each species’ song audible in golden-crowned sparrow nests and showed that even in a relatively small area, the ratio of heterospecific to conspecific song exposure varies from 0 to 20%. We then asked whether natural exposure to more frequent or louder heterospecific song explained any variation in golden-crowned nestling response to heterospecific song playbacks. In a population where sister species, golden-crowned and white-crowned sparrows, breed syntopically, we found that nestlings discriminate between heterospecific and conspecific song playbacks prior to the onset of song memorization. Thus, it remains unknown whether natural variation in acoustic exposure prior to song learning affects the template for recognition. Because birds are capable of hearing birdsong very early in life, early exposure to song could plausibly affect recognition of appropriate models however, this idea conflicts with the traditional view that song learning occurs only after a bird leaves the nest. Young songbirds face a challenging task: how to recognize and selectively learn only their own species’ song, often during a time-limited window. Oscine songbirds are an ideal system for investigating how early experience affects vocal behavior. 2School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States.1Department of Biological Sciences, Vanderbilt University, Nashville, TN, United States. ![]() Hudson 1* Nicole Creanza 1 Daizaburo Shizuka 2 ![]()
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