Female zebra finches learn to prefer more than one song and from more than one tutor

Abstract

Birdsong is a culturally transmitted mating signal: young birds learn specific variants of species-specific song(s) from conspecific models. Female song preferences are also learned early in life, but despite the potential functional implications of such learned mating preferences, we still have a poor understanding of when and from whom females learn. This also holds true for one of the foremost models of vocal learning, the zebra finch, Taeniopygia guttata. Both male and female zebra finches memorize their tutor's song motif: as adults, males will sing and females prefer their tutor's song. We here tested whether juvenile females would also learn to prefer the songs of several individuals, and whether the timing and propensity of song preference learning were condition dependent. Young females raised and cross-fostered in experimentally manipulated brood sizes were exposed to several model songs: first their foster father's song until nutritional independence (days 0e35) and then as subadults to playbacks of two different tutor songs (days 35e65). As adults, females preferred all three model songs over unfa-miliar songs. There were no interaction effects between females' early rearing conditions (brood size) and preference strength for the different tutor songs. An additional live-tutored group had equally strong preferences for the foster father's song (only heard before day 35) as the tape-tutored females. The combined results demonstrate that subadult females memorize several song types during different times of development and as adults prefer these songs over unfamiliar songs. These findings imply that multiple song learning needs to be taken into account for avian mate choice studies even in species that lack song type repertoires but show individual differences in song. O 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved. Learned mating preferences are increasingly recognized as an evolutionary force but to estimate their qualitative and quantitative impact on population dynamics, the strength and direction of learned versus experience-dependent preferences need to be bet-ter documented (e.g. Verzijden et al., 2012) in order to improve modelling approaches (Lachlan & Nowicki, 2012). In songbirds (oscines), (learned) song is an important mating signal (Catchpole & Slater, 2008) but while the process of (male) song learning is relatively well studied, our understanding of female song produc-tion and preference learning lags behind in all aspects (Kroodsma, Vielliard, & Stiles, 1996; Riebel, 2003b; Riebel, Hall, & Langmore, 2005) although the 'when' and 'from whom' females learn their preferences have turned out to be crucial parameters in theoretical models for the evolution of learned birdsong (Lachlan & Nowicki, 2012; Ritchie, Kirby, & Hawkey, 2008). Zebra finches, Taeniopygia guttata, are one of the few species in which song acquisition in females has seen some systematic study (for reviews see Riebel, 2003a, 2009). Complex courtship song in zebra finches is pro-duced only by adult males: each male sings an individually distinctive song motif that closely resembles an adult song model (the 'tutor song'). As shown by sequential exposure to different tutors, the peak of the sensitive phase for (male) song production learning is between 35 and 65 days posthatching (Slater, Eales, & Clayton, 1988). Although females do not sing, several experi-mental studies have shown that females learn about songs as ju-veniles too: after maturation, which can be as early as 100 days (Zann, 1996), adult females have been shown to prefer the song of the adult male with which they had been housed between 35 and 65 days posthatching over the song of an unfamiliar male, showing cultural transmission of song preferences is possible along nonge-netic lines (Clayton, 1988, 1990; Miller, 1979; Riebel, Smallegange, Terpstra, & Bolhuis, 2002). Song preferences in female zebra finches have been validated as predictors of live male preferences and mating decisions (for a review see Riebel, 2009). Cross-fostering between the subspecies T. g. guttata and T. g. castanostis has shown that females not only learn preferences for specific songs but also generalize some of the subspecies' structural