Song ontogeny in Nuttall's white-crowned sparrows tutored with individual phrases.

Behavioral ontogeny involves the interaction of innate predispositions and experience. In bird song learning, one approach to exploring this interaction is to examine the songs rehearsed by young birds whose exposure to tutor models has been carefully controlled. Here, I analyzed the rehearsed repertoire in Nuttall's white-crowned sparrows (Zonotrichia leucophrys nuttalli) tutored with individual phrases of conspecific and heterospecific songs. The proportions of phrase types rehearsed indicate that the learning biases evident in crystallized song are manifest early on, suggesting preferential memorization rather than preferential retention during attrition. The proportion of songs beginning with whistles increased during song rehearsal and phrase sequence variability decreased, consistent with the idea that innate syntax specifications guide song rehearsal. Single-phrase tutored birds overproduced phrases to the same extent previously observed in birds tutored with full, normal song but retained fewer phrase types in their crystallized repertoires. This suggests that in this subspecies, acquired syntax information does not affect the number of phrase types memorized and rehearsed but does affect repertoire attrition at the end of the sensorimotor phase. I discuss these results with a focus on the action of innate templates in song development and subspecies differences in this process.