A comparative approach to vocal learning: intraspecific variation in the learning process

Abstract

Vocal learning in birds often results in geographically distinct ‘dialects’. To examine whether genetic variation underlies intraspecific differences in vocal development, young male white-crowned sparrows from sedentary ( Zonotrichia leucophrys nuttalli) and migratory ( Z. l. oriantha ) populations were reared in standardized conditions in the laboratory, and tutored throughout the first year of life with a changing roster of tutor songs. Male nuttalliacquired their tutor imitations at a later age, and over a broader range of ages, than did orianthamales. All males eventually crystallized a single song type, but male orianthasang imitations of more tutor songs in plastic song, and persisted in plastic song twice as long as nuttallimales. Nuttalliimitations of tutor songs were fragmentary, but their imitations of specific syllables were more accurate than those of oriantha. These genetically based differences in vocal learning may be different strategies to achieve song matching with territory neighbours in migratory and sedentary populations. Young migratory orianthaface a shorter singing season during the early sensitive phase for song acquisition and greater uncertainty over where they will breed as yearlings relative to nuttallimales, who may occupy territories relatively closer to their birthplace, and may settle as early as their first autumn. Male orianthaacquire several song dialects when young, and then, through a process of selective attrition, retain the song that matches the local dialect where they settle to breed. In contrast, nuttallimay retain the ability to acquire an accurate song copy from a neighbour when they establish a territory.