Nutrition and peer group composition in early adolescence: impacts on male song and female preference in zebra finches

Abstract

There is increasing evidence that learning processes contribute to variation in sexually selected traits, but their potential condition dependence is poorly understood. Birdsong is a learned, culturally transmitted mating signal where suboptimal developmental conditions impair song development, thus demonstrating that learned signals can show condition dependency. However, song learning is also contingent on conspecific song models, raising the question of potential synergistic effects of nutrition and social environment on song development. Zebra finches, Taeniopygia guttata, have been instrumental in testing how stressors experienced during the first month of life (i.e. before nutritional and social independence) affect song learning (developmental stress hypothesis). However, the critical phase for male song learning and female song preference learning is the second month of life, when juveniles start foraging independently and are joining larger social groups. This raises the question of how diet and peer group composition during this adolescent stage affect male song and female song preference development. To test these questions, postfledging juveniles were housed in peer groups of varying sex ratios and fed low- or high-quality diets. Diet interacted with social conditions (sex ratio) in affecting male song rate and female song preferences but, foremost, the social environment shaped song and preference in previously unreported ways: despite the availability of an adult model, male song showed more similarity with the song of their former peers than with their respective tutor. Likewise, females, as adults, showed significant preferences for songs of their former peers over unfamiliar song but not for their respective tutor: the first demonstration of horizontal transmission of song preferences in female zebra finches. These results highlight how the quality of the rearing environment and social factors affect birdsong learning, contributing towards the growing evidence for developmental plasticity at different life stages of both mating traits and preferences.